Mate choice games, context-dependent good genes, and genetic cycles in the side-blotched lizard, Uta stansburiana

According to mate choice models, a female should prefer males with traits that are reliable indicators of genetic quality which the sire can pass on to their progeny. However, good genes may depend on the social environment, and female choice for good genes should be context dependent. The side-blotched lizard, Uta stansburiana, exhibits genetically based throat colors (orange, blue, or yellow) that could be used as a sexually selected signal since they reliably predict the genetic quality of mates. The frequencies of male and female morphs cycle between years, and both male and female morphs have an advantage when rare; thus genetic quality will depend on morph frequency. A female should choose a sire that maximizes the reproductive success of both male and female progeny. We examine a game theoretical model that predicts female mate choice as a function of morph frequency and population density. The model predicts the following flexible mate choice rule: both female morphs should prefer rare males in ’boom years’ of the female cycle (e.g., ’rarest-of-N rule’), but prefer orange males in ’crash years’ of the female cycle (’orange-male rule’). Cues from the current social environment should be used by females to choose a mate that maximizes the future reproductive success of progeny, given the social environment of the next generation. We predict that the cue is the density of aggressive orange females. In the side-blotched lizard, cycling mate choice games and context-dependent mate choice are predicted to maintain genetic variation in the presence of choice for good genes. Received: 8 March 2000 / Revised: 26 August 2000 / Accepted: 4 September 2000     

Lack of innate preference for morph and species identity in mate-searching <Emphasis Type="Italic">Enallagma</Emphasis> damselflies

Insect mate recognition is often viewed as stereotypic, innate, and species-specific. However, male damselflies can learn to identify female-specific color morphs as potential mates. A suite of male mimicry hypotheses assume that heteromorphic females, which differ from males in color pattern, are more easily recognized as “female” and thus lack the inherent, anti-harassment advantage that the more male-like signal provides for andromorphs. Using two measures of male preference, we investigated whether naïve males have a preexisting sensory bias for a given morph color in Enallagma civile, a species that appeared to exhibit extreme plasticity in morph expression across generations within a breeding season. E. civile males raised in the absence of females exhibited no preference for either morph, whereas males raised with one female type exhibited a learned sensory bias for that morph. Male Enallagma also lacked a bias toward conspecific females over a congeneric sister species. In a naturally naïve population of Enallagma ebrium, males reacted sexually to both morphs of Enallagma hageni as often as they did to conspecific females, whose thoracic spectra were nearly identical with those of E. hageni. Moreover, despite the similar thoracic spectra of males and andromorphs, both of which reflected UV, males rarely reacted sexually to other males. Our results falsified implicit assumptions of male mimicry hypotheses, supported learned mate recognition, and suggested a scenario for speciation via sexual conflict.     

Social,environmental and genetic factors in the ontogeny of phenotypic differentiation in a lizard with alternative male reproductive strategies

Summary Adult male tree lizards, Urosaurus ornatus, practise alternative (territorial or sneaker/satellite) reproductive strategies that are correlated with differences in throat color and body size. In this study we raised tree lizards from hatching in the laboratory to examine the question of whether the phenotypic expression of secondary sex coloration and body size can be facultatively influenced by social or abiotic environmental factors. We compared males reared in the laboratory under different social and environmental conditions to males in the field and found no effect of different conditions on phenotypic differentiation (Figs. 2–4). Thus, phenotypic differences between morphs probably result largely from nonfacultative expression of different genotypes. This suggests that alternative male morphs practise a mixed evolutionary stable strategy (ESS) rather than one morph making the best of a bad situation. However, in the context of ESS theory it is difficult to explain our further result that the nonterritorial morph in this species grows faster and reaches a larger adult body size than the territorial morph (Fig. 5).     

Activity budgets in two species of bee flies (Lordotus: Bombyliidae,Diptera): a comparison of species and sexes

Summary This study compares time budgets of males and females of two sympatric species of bee flies, Lordotus pulchrissimus and L. miscellus. These species occur synchronously in sand dune habitat on the north shore of Mono Lake, Mono Co., California, and feed almost exclusively on the flowers of a composite shrub, Chrysothamnus nauseosus. The two closely related species, with similar ecological requirements and in an identical environment, allocate time and energy in very different ways, even when accomplishing the same ecological goals. L. pulchrissimus males and females engage respectively in aggressive interactions and feeding primarily in the morning. In contrast, L. miscellus males and females intersperse brief periods of resting with flying when defending territories and feeding, and they keep up these activities until later in the day. Similarly within species, males are involved in aggressive interactions for a shorter period each day, and females feed over a longer period. Flies in all sex-species classes but male pulchrissimus allocate their time energetically in similar ways. Male pulchrissimus spend more time each day in energetically costly activities; they engage in continuous hovering flight and intense interactions in aerial aggregations. While male miscellus feed little, male pulchrissimus spend a large portion of their time feeding, approximately as much as females, contrary to the expectation that males should be foraging-time minimizers. This study corroborates the conclusions of previous studies on bee-fly communities by showing that nectar and pollen are important resources for adult bee flies, at least for some species: Individuals of these two species spend a large proportion of their adult lifetimes feeding.     

Frequency-dependent male mate harassment and intra-specific variation in its avoidance by females of the damselfly Ischnura elegans

We focused on male harassment on different female color morphs of the damselfly Ischnura elegans and on variation in morph-specific mating avoidance tactics by females. In I. elegans, one of the female morphs is colored like the conspecific male (andromorphs) while the other morphs are not (gynomorphs). Our first goal was to quantify morph-specific male mating attempts, hence male harassment, in populations with manipulated population parameters (densities, sex ratios, and proportion of andromorphs). Second, we examined the female's perspective by looking for potential differences in morph-specific mating avoidance tactics and success of those tactics in a natural population. Differences in population conditions did influence the number of male mating attempts per morph. The less frequent female morph was always subject to fewer mating attempts, which contradicts earlier hypotheses on mimicry, but supports those that assume that males learn to recognize female morphs. Gynomorphs occupy less open habitat and often fly away when a male approaches, while andromorphs use more open habitat, do not fly large distances and directly face approaching males. Female morphs did not differ in the proportion of successful mating-avoidance attempts. Our results suggest that the maintenance of the color polymorphism is most probably the result of interactive selective forces depending on variation in all population conditions, instead of solely density- or frequency-dependent selection within populations.     

Tests of the harassment-reduction function and frequency-dependent maintenance of a female-specific color polymorphism in a damselfly

Color polymorphisms have provided classical examples of how frequency-dependent selection maintains genetic variation in natural populations. Here we tested for the first time, the hypothesized adaptive function of a female-specific color polymorphism in odonates to lower male harassment towards females generally. Under conditions controlling for sex ratio, population density and morph frequency, we also tested two major frequency-dependent selection hypotheses for the maintenance of the polymorphism. Using groups of captive Enallagma hageni, whose females are either green or a male-like blue, we varied morph frequency at two sex ratios. We quantified sexual harassment towards females by visual observations, and by the presence of dust on females that was transferred from dusted males. Per capita harassment rate for the female-monomorphic treatments did not differ from that of the female-polymorphic treatments. At a male-biased sex ratio, per capita harassment rate towards blue, but not green females increased with morph frequency, providing partial support for frequency-dependent selection resulting from male learning of female morphs. Even at high frequency, green females were not harassed more than blue, contrary to the prediction that males should always recognize green females as mates. Moreover, frequency-dependent harassment towards blue females was not detectable using harassment measured with dust evidence, which greatly underestimated the incidence of sexual harassment. Our findings identified problems with the use of insectaries and the dusting technique to quantify male sexual harassment towards females, as well as with a past insectary experiment on Ischnura elegans that failed to demonstrate frequency-dependent harassment.     

Alternative male mating tactics in a cichlid, Pelvicachromis pulcher: a comparison of reproductive effort and success

Pelvicachromis pulcher is a small African cichlid which breeds in holes. Males may either reproduce monogamously (pair males), polygynously (harem males), or be tolerated as helpers in a harem territory (satellite males). These helpers share in defence of the territory against conspecifics, heterospecific competitors and predators. There are two male colour morphs that are fixed for life and are apparently genetically determined. These differ in their potential mating strategy. Red morph males may become harem owners, while yellow morph males may become satellite males, and males of both morphs may alternatively pair up monogamously. We compared the reproductive effort and success of these three male reproductive strategies. Effort was measured as attack rates, time expenditure and the risk of being injured or killed when attacking competitors or predators of three sympatric fish species. Reproductive success was measured by observing how many eggs were fertilized by each male when this was possible, and by using genetic markers. The number of fry surviving to independence of parental care was used as a criterion of success. The reproductive success of harem males was 3.3 times higher than that of pair males and 7 times higher than that of the average satellite male. Dominant satellite males, however, were as successful as monogamous pair males, using the measure of fertilized eggs. To our knowledge, this has not been found previously in any fish species. Both harem and pair males had lower parental defence costs per sired offspring, however, than males using the alternative satellite tactic. Defence effort was significantly related to the risk of injury. Received: 17 January 1996 / Accepted after revision: 9 June 1997     

Parental care of nestlings by male red-winged blackbirds

Summary Nestling feeding by males is less common among birds with polygynous mating systems than in monogamous species, because of the pronounced trade-off between parental behavior and the attraction of additional mates. In this study, however, we found that male red-winged blackbirds (Agelaius phoeniceus) commonly assisted females in feeding nestlings in several Ontario marshes. Male parental care was additional to that provided by females, and it significantly enhanced the fledging success of nests (Table 2). Male redwings did not help to feed all nests on their territories: primary and secondary nests were much more likely to receive male parental care than tertiary and later nests. Contrary to expectation, male parental care was not restricted to the nests of primary females: a greater proportion of secondary than primary nests were assisted (Tables 4a and b). The presence of new females settling on the territory at the same time that a resident female had nestlings, resulted in males deferring parental care until a later brood. This suggests that males trade off the recruitment of females against parental care to an existing brood. Although the number of nestlings fledging from a male's territory was strongly influenced by the number of females in the harem, males could additionally increase their reproductive success by feeding nestlings in one or more nests on their territories (Fig. 2). The reproductive success of females was significantly enhanced by male assistance in feeding nestlings (Table 3). However, those females not receiving male assistance on territories of feeding males did not suffer a significantly reduced reproductive success in comparison to females on territories of non-feeding males (Table 2). Males varied considerably in the quality of brood care given. We therefore suggest that the quality of male parental care may be a factor considered by females in choosing a breeding situation.     

Environmental and genetic determinants of the male forceps length dimorphism in the European earwig Forficula auricularia L.

Male dimorphisms are particularly conspicuous examples of alternative reproductive strategies. The male forceps length dimorphism in the European earwig Forficula auricularia has long been considered an example of a status- (body size) dependent male dimorphism. In this paper, I test three hypotheses relating to the dimorphism of F. auricularia. First, that the dimorphism is status dependent and determined by nutrition. Second, that the dimorphism is a density-dependent adaptation. Third, that there is a genetic basis to population differences in morph frequency seen in the field. These hypotheses were tested by rearing two populations in a split-family rearing design with two diets and two densities. Populations of male earwigs reared in the common garden differed in forceps length and relative forceps length. The populations also differed in the morph frequencies, with 40 versus 26% long-forceped males. These results confirm the notion that there is a genotype-by-environment interaction that determines the morph frequency in a population. There were only minor effects of density on male forceps length and no influence of density on the male dimorphism. In accordance with the hypothesis that the morphs are status-dependent alternatives, large-forceped males only arose on the high-protein diet that produced earwigs of a large body size. However, not all large males produced the long-forceped phenotype. I put forward an extension of the status-dependent dimorphism model that may account for the pattern of forceps dimorphism in this species. Received: 18 November 1998 / Received in revised form: 14 May 1999 / Accepted: 25 July 1999     

Dimorphism and possible sex change in copepods of the family Calanidae

Adult females of 14 of 25 species of the family Calanidae were found to be dimorphic with respect to the number of aesthetases on the first antenna. The trithek morph, in which most antennal segments bear a complement of one aesthetasc and two setae, appears to be the typical female phenotype. The quadrithek morph is less common and, as in males, odd-numbered segments 2b, 3, 5, 7 and 9 carry quadritheks, i.e., two aesthetascs as well as two setae. Segment 21 in the quadrithek female bears an aesthetasc that is absent in the trithek female. Male antennal segments are distinguished from those of trithek and quadrithek females by pronounced morphological differences in aesthetasc shape and size as well as fusion of one or more pairs of antennal segments. The quadrithek morph usually comprised only a small proportion (<10%) of a local population. Quadrithek morphs were found in tropical and subtropical genera (Cosmocalanus and Nannocalanus), broadly ranging genera (Calanoides), as well as in cool-water lineages (Calanus s.s., Calanus s.l. cristatus, C. s.l. plumchrus, C. s.l. propinquus and C. s.l. tonsus). Maximum frequencies of quadrithek morphs (10 to 12%) in Calanus pacificus californicus occurred during the upwelling season from late winter into spring. No indication of sexual or antennal dimorphism was found in CV C. pacificus californicus sexed by examination of gonad and gonaduct. The quadrithek dimorph appears to be the product of sex change by the larger-sized late-juvenile potential male. The evolutionary and ecological significance of this presumptive hypothesis is that the larger-sized potential male reaching adulthood one or more weeks before maturation of genotypic females may increase its reproductive output by sex change in the course of the final molt to mature as a functional female. Given the sex-change hypothesis, morphogenesis of secondary sexual structures would appear to be controlled by androgenic-like secretions from the genital tract, as has been shown in malacostrocans.     

Paternal care in the European starling,Sturnus vulgaris: nestling provisioning

The extent to which male birds in polygynous species with biparental care assist in nestling feeding often varies considerably between nests of different mating status. Both how much polygynous males assist and how they divide their effort between nests may have a profound effect on the evolution of mating systems. In this study we investigated how males in the facultatively polygynous European starling Sturnus vulgaris invested in their different nests. The amount of male assistance affected the quality of the offspring. Polygynous males invested as much as monogamous males, but divided their effort asymmetrically between nests, predominantly feeding nestlings of first-mated (primary) females. Although females partly compensated for loss of male assistance, total feeding frequency was lower at primary females’ nests than at monogamous females nests. Secondary females received even less assistance with nestling rearing, and the extent to which males assisted decreased with the length of the interval between the hatching of the primary and secondary clutches. These results are contrasted with those from a Belgian populations of starlings with a much more protracted breeding season and thus greater opportunities for males to attract additional mates during the nestling rearing period. The results show that both the “defence of male parental investment model” and the “asynchronous settlement model” have explanatory power, but that their validity depends on the potential length of the breeding season. Received: 21 July 1995/Accepted after revision: 13 July 1996     

Female cannibalism and male courtship tactics in threespine sticklebacks

Summary Female threespine sticklebacks (Gasterosteus aculeatus) frequently raid male nests and eat all the eggs therein. We tested the hypothesis of Vickery et al. (1988) that females prefer to raid nests containing large numbers of eggs than ones with smaller numbers of eggs. This hypothesis is based on the finding that females spawning in nests containing many eggs will have reduced hatching success because of egg crowding. By consuming the male's eggs and forcing him to rebuild his nest, raiding females might obtain a new opportunity to spawn under better conditions. Our results were consistent with the first prediction of this hypothesis that females were more likely to spawn in nests containing fewer eggs than in nests with many eggs. However, this may be the result of males becoming less receptive to females as the number of eggs in their nests increases. Prediction 2 was that females should raid those nests containing the most eggs. Contrary to this prediction, males defending only one clutch were as likely to have their nests raided by groups of females as males defending several clutches of eggs. Female cannibalism is therefore unlikely to have evolved as a means of gaining access to a male defending a small number of eggs. We also examined the tactics used by males to counter female raids. Most raids occur when the male is courting, and nests are more vulnerable to shoals of females than to single females. Therefore, we hypothesized that males with eggs preferentially court a single female rather than large groups of females, and that males without eggs court both groups indiscriminately. We also predicted that males restrict the number of females they mate with when risk of having their nest raided is high. Our results indicate that: (1) both males with eggs and those without eggs minimize the risk of female cannibalism by courting solitary females rather than groups of females and (2) males limit the number of females that lay eggs in their nest when several potentially raiding females are present. Offprint requests to: G.J. FitzGerald     

The artistic three-spined stickleback (<Emphasis Type="Italic">Gasterosteous aculeatus</Emphasis>)

We investigated whether female three-spined sticklebacks ( Gasterosteus aculeatus) are more attracted to a male whose nest contains colourful artificial material than to a nest that only contains algae. The purpose was to examine whether nest characters are of importance for female choice in the three-spined stickleback. Most studies on female preference in this species have focused on male morphological traits. In our study, on a marine population of three-spined stickleback on the West coast of Sweden, we found that males marked their nests' entrance with a deviant colour of algae — an apparent decoration. Moreover, males also decorated their nests with shiny and colourful foil sticks and spangles when provided with such, thereby apparently reducing the nest camouflage. In a mate choice experiment, females were more attracted to males with nests containing sticks and spangles than to males with undecorated nests. Nest decoration may be important for the evolution of paternal care in this species: if males advertise their paternal skills by ornamenting their nest they will receive more matings than males with dull nests.     

Costs of brood parasitism and the lack of defenses on the yellow-winged blackbird - shiny cowbird system

The shiny cowbird (Molothrus bonariensis) is a generalist brood parasite that lays either white-immaculate or spotted egg morphs in eastern Argentina and Uruguay. Some hosts accept both morphs, others accept spotted eggs and reject the white morph, but no host has been found to accept white eggs and reject spotted ones. It has been suggested that the yellow-winged blackbird (Agelaius thilius) may be that type of host. The finding of a white acceptor-spotted rejector species would help to explain the occurrence and maintenance of the parasite egg polymorphism. We studied the incidence of shiny cowbird parasitism on this host, its costs for their reproductive success and the presence of antiparasitic defenses in the yellow-winged blackbird - shiny cowbird system. The parasite affected the reproductive success of the host in two ways. Cowbirds punctured host eggs causing a reduction in clutch size, and yellow-winged blackbirds deserted their nests whenever they suffered high egg loss. In addition, parasitized nests suffered higher predation during the nestling stage, but not during egg stages, indicating that the difference found was related to the presence of the cowbird chick, and not to higher exposure of parasitized nests to both parasites␣and predators. Despite the costs imposed by the parasite, yellow-winged blackbirds have not evolved antiparasitic defenses. This host did not reject any egg morph of the shiny cowbird nor desert parasitized nests unless it had suffered high egg loss. Current explanations for the host lack of defenses, the “time lag” and the “equilibrium” hypothesis, are discussed. Received: 29 August 1997 / Accepted after revision: 10 January 1998     

Color patterns of the shrimps Heptacarpus pictus and H. paludicola (Caridea: Hippolytidae)

Color patterns of the shallow-water shrimps Heptacarpus pictus and H. paludicola are formed by chromatosomes (usually termed chromatophores) located beneath the translucent exoskeleton. Development of color patterns is related to size (age) and sex. The color expressed is determined by the chromatosome pigment dispersion, arrangement, and density. In populations with well-developed coloration (H. pictus from Cayucos, California, 1976–1978, H. paludicola from Argyle Channel, San Juan Island, Washington, June–July, 1978), prominent coloration was a characteristic of maturing females, breeding females, and some of the larger males. In the Morro Bay, California, population of H. paludicola (sampled 1976–1978), color patterns were poorly developed except in a few large females. In both species, most shrimp lose color at night because of pigment retraction in certain chromatosomes. In both species, there are 5 basic morphs: 1 transparent and 4 colored morphs. In the colored morphs, the color patterns are composed of bands, stripes, and spots which appear to disrupt the body outline. Each color morph also has a common environmental color in its color pattern, e.g the green of green algae, the whites and pinks of dead and living coralline algae, and various shades of tidepool litter. These shrimps are apparently under heavy predation pressure by fish, and it is suggested that the color patterns are camouflage against such visually-hunting predators.     

Alternative reproductive tactics and male-dimorphism in the horned beetle Onthophagus acuminatus (Coleoptera: Scarabaeidae)

Adult dung beetles (Onthophagus acuminatus) exhibit continuous variation in body size resulting from differential nutritional conditions experienced during larval development. Males of this species have a pair of horns that protrude from the base of the head, and the lengths of these horns are bimodally distributed in natural populations. Males growing larger than a threshold body size develop long horns, and males that do not achieve this size grow only rudimentary horns or no horns at all. Previous studies of other horned beetle species have shown that horned and hornless males often have different types of reproductive behavior. Here I describe the mating behaviors of the two male morphs of O. acuminatus during encounters with females. Females excavate tunnels beneath dung, where they feed, mate and provision eggs. Large, horned males were found to guard entrances to tunnels containing females. These males fought with all other males that attempted to enter these tunnels. In contrast, small, hornless males encountered females by sneaking into tunnels guarded by other males. In many instances, this was accomplished by digging new tunnels that intercepted the guarded tunnels below ground. Side-tunneling behavior allowed sneaking males to enter tunnels beneath the guarding male, and mate with females undetected. Both overall body size and relative horn length significantly affected the outcome of fights over tunnel ownership. These results suggest that alternative reproductive tactics may favor divergence in male horn morphology, with long horns favored in males large enough to guard tunnels, and hornlessness favored in smaller males that adopt the “sneaking” behavioral alternative. Received: 12 October 1996 / Accepted after revision: 8 August 1997     

Ecological and physiological differences between two colour morphs of the coral Pocillopora damicornis

Pocillopora damicornis (Linnaeus) is a ubiquitous branching coral found throughout the Indo-Pacific region. Like many other species of coral, P. damicornis displays a large range of morphologies. At One Tree Island, it occurs as two distinct morphs that are easily distinguished by the presence or absence of pink pigmentation. The two colour morphs of P. damicornis were found to differ in their distribution and abundance in the One Tree Island Lagoon. The brown morph was more abudant than the pink morph in the shallows (<1 m),whereas the pink morph was more abundant at deeper sites (>3 m). The two morphs also differed physiologically. The brown morph tended to have a greater calcification rate than the pink morph, regardless of environmental conditions. However, the difference in the calcification rate between the two morphs became non-significant under shaded conditions (5% full sunlight), indicating some degree of physiological plasticity of the morphs. The pink colour in P. damicornis was due to a hydrophilic pigment with a major peak absorbance at 560 nm. The expression of pink pigment had both genetic and phenotypic components. The brown morph has a reduced genetic capacity to express the pigment relative to the pink morph. On the other hand, pigment expression could be induced by light in the pink morph. Although genetic differences ultimately determine the differences between the two morphs of P. damicornis, the extent of pigment expression is under some degree of environmental influence.     

Adult female hamsters avoid interspecific mating after exposure to heterospecific males

When females mate with a heterospecific male, they do not usually produce viable offspring. Thus, there is a selective pressure for females to avoid interspecific mating. In many species, females innately avoid heterospecific males; females can also imprint on their parents to avoid later sexual interactions with heterospecific males. However, it was previously unknown whether adult females can learn to discriminate against heterospecific males. We tested the hypothesis that adult females previously unable to avoid interspecific mating learn to avoid such mating after being exposed to heterospecific males. Syrian hamster (Mesocricetus auratus) females not previously exposed to Turkish hamster (Mesocricetus brandti) males can discriminate between odors of conspecific and heterospecific males, but they mate with either type of male. However, when we exposed adult females to both a conspecific male and a heterospecific male through wire-mesh barriers for 8 days, and then paired them sequentially with the two males, females were more receptive to conspecific males and more aggressive to heterospecific males. When females were paired with the heterospecific male first and the conspecific male second, no female was receptive and all were aggressive to heterospecific males. When females were paired with the conspecific male first, only 43% of females were then aggressive toward the heterospecific male. That is, interactions with conspecific males may decrease a female’s ability to properly avoid heterospecific males. Our study clearly shows for the first time that females can learn during adulthood to avoid interspecific mating just by being exposed to stimuli from heterospecific males.     

Reproductive consequences of male body mass and aggressiveness depend on females’ behavioral types

Relatively few investigations explicitly test for concordant versus conflicting selection pressures from intrasexual versus intersexual selection. Here, we examine the effects of male body mass and behavioral type (BT) on reproductive success in the spider Anelosimus studiosus, with emphasis placed on the potential interaction between intrasexual and intersexual selection influences. Female A. studiosus exhibit either an aggressive-active or docile-passive BT, both of which co-occur in multifemale colonies. Males, in contrast, exhibit a more continuous distribution of behavioral tendencies. We investigated the male traits favored by females in five trial types: one docile female, one aggressive female, four docile females, four aggressive females, and two docile and two aggressive females. Male reproductive success was estimated by the number eggs produced by females following staged mating trials. In previous work, it was established that large aggressive males are favored in male–male contests, an intrasexual effect. However, large aggressive males were not universally favored here. We failed to detect an effect of male body mass or aggressiveness on reproductive success in trials with all docile females; however, in situations involving aggressive females, large aggressive males experienced diminished reproductive success relative to small docile males. Large, aggressive males were also more likely to be attacked and killed by aggressive females in the first 20 min of staged encounters and were more likely to be found dead after 72 h of unobserved interactions. Taken together, our data suggest that the reproductive consequences of male traits differ based on (1) the aspect of sexual selection being considered (intrasexual versus intersexual) and (2) the BT of their prospective mates: large aggressive males enjoy advantages in intrasexual selection and when courting docile females and small docile males experience reduced risk of cannibalism and increased reproductive success with aggressive females.     

Distribution pattern, reproductive traits, and molecular analysis of two coexisting vermetid gastropods of the genus Petaloconchus: a Caribbean endemic and a potential invasive species

Vermetid gastropods are characterized by complex taxonomy and unusual ecology. A survey of the fouling community in the intake channel at the Planta Centro Power Plan in Puerto Cabello, Venezuela, found massive colonies of vermetid gastropods of the genus Petaloconchus. We arbitrarily named two prevalent varieties as black and brown-orange morphs, distinguishing based on the color of their soft bodies. Spatial distribution was different for the morphs. The black morph was present along the jetty, with higher average densities in the shallower intertidal area (410 vs. 143 ind m⁻²), while the brown-orange morph was only present at the initial part of the channel (μ = 83 ind m⁻²). Both produced small eggs (142 vs. 180 μm diameter on average), with the orange-brown eggs being slightly larger, but the morphs differed in other reproductive aspects. The brown-orange morph produced significantly fewer capsules (up to nine simultaneously per female) with fewer embryos (average of 27 viable embryos/capsule) that hatched at a larger size (577 μm on average), allocating about 17.64% of the initial egg production to nurse eggs. In contrast, the black morph produced up to 14 capsules simultaneously, hatched an average of 178 veligers of 212 μm, and produced no nurse eggs. The intra-capsular development reached a more advanced stage in the brown-orange morph than in the black one. Several cytochrome subunit I (COI) and 16S rRNA (16S) haplotypes were found for the black morph, when compared to only one haplotype for both genes present for the brown-orange morph. Preliminary phylogenetic analyses separated the morphs into different clades, supported by robust bootstrap values and posterior probabilities (>98). Our results indicate that the morphs are two different species: the black morph was identified as Petaloconchus cf. varians and the brown-orange morph as a non-described species, Petaloconchus sp. (orange). The first is endemic to the Caribbean, while the second is potentially an introduced species.