Forced copulation as a conditional alternative strategy in camel crickets

In the animal kingdom, males typically acquire reproductive access to females through courtship, nuptial gifts, or combat. In many species, small or poor-condition males that are unable to produce an attractive display, proffer an adequate mating gift, or dominate in male–male competition may resort to forced copulation. Forced copulation has been previously demonstrated in the camel cricket Pristoceuthophilus marmoratus and is uniquely facilitated by male hind leg weaponry that functions in both intrasexual competition and sexual coercion. Because male leg armaments are positively allometric, the largest males would seem best equipped to force-copulate, although they might be the most attractive to females, and so least likely to adopt a forced copulation strategy. In order to resolve this potential paradox and determine which males are in fact most likely to force-copulate, we manipulated male body size using diet and performed mating trials. Results showed that (1) male size increased with diet quality, (2) females appear to prefer larger males, and (3) smaller males were more likely to attempt forced copulation. Our results thus suggest that forced copulation is a condition-dependent alternative mating tactic used by small males unattractive to females.     

Fluctuating asymmetry,interspecific aggression and male mating tactics in two species of Japanese scorpionflies

Summary Fluctuating asymmetry (FA) is defined as small, random deviations from bilateral symmetry in a generally perfect bilaterally symmetrical morphological trait. FA in forewing length affects the outcomes of interspecific contests for food items (dead arthropods) between two species of Japanese scorpionflies, Panorpa nipponensis and P. ochraceopennis, in nature. FA differences between same-sex contestants are more important than either body size or ownership of food in determining the outcomes of interspecific contests; for both sexes, winners statistically significantly more often have relatively low FA. Two condition-dependent mating tactics are used by the males of each species: (a) a male may defend a dead-arthropod nuptial gift, or (b) a male without such an arthropod may wait near a male with one. In both tactics, males release long-distance sex pheromones. Groups of pheromone-releasing males are made up of one male with a nuptial gift and his satellites; the males in a group may be conspecifics or heterospecifics. Males that lose contests for nuptial gifts often become satellites of the contest winners whether or not winners are conspecific. Satellite males have statistically significantly greater FA than males with nuptial gifts in heterospecific male display groups. Satellite males mate infrequently and briefly compared to resource-holding males. Satellites of heterospecific males copulate with conspecific females displaced from nuptial gifts by the resource-holding males of the other species. In both species, the largest and smallest individuals have the greatest FA, and intermediate-sized individuals have the least; this same pattern often occurs in other animals.     

Experience-dependent choices ensure species-specific fragrance accumulation in male orchid bees

Male neotropical orchid bees (Euglossini) collect volatile chemicals from orchid flowers and other sources and store them in hind leg cavities. The accumulated fragrance bouquets are later emitted at mating sites. Although most other insects synthesize pheromone blends de novo, specific euglossine perfumes are derived from active choices in a changing fragrance market. Male bees of three species of Euglossa possessed distinctive fragrance phenotypes showing little variation by locality and habitat in mainland Central America. In cage experiments, fragrance choice by male Euglossa imperialis was influenced markedly by a bee's collection history. Collection of a given chemical strongly reduced its attractiveness on subsequent occasions, an effect that was retained over days. Experimentally adding the chemicals directly to bee hind legs produced no effect. We conclude that bees learn and remember chemicals they collect. Innate odor preferences, memory and the avoidance of overcollecting by negative feedback may be the primary mechanisms that ensure unique blends of pheromone analogs in these tropical forest bees.Supplementary material is available in the online version of this article at and is accessible for authorized users.An erratum to this article can be found at     

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     

“Alternative” mating behavior in the swordtails Xiphophorus nigrensis and Xiphophorus pygmaeus (Pisces: Poeciliidae)

Summary The swordtail Xiphophorus nigrensis exhibits three relatively discrete male body-size classes that derive from allelic variation at the Y-linked pituitary (P) locus. Previous studies have shown that larger males have greater relative reproductive success, and that females prefer large males. We describe the mating behavior utilized by males of each size class during individual encounters with females. Small males rely on chase behavior, similar to the alternative mating behavior classified as sneaker in small males of other species. Large males court and intermediate-sized males court or chase, depending on their body size. There is a strong correlation between P alleles for small size (s) and large size (L) with chasing and courting, respectively. The relationship between mating behavior of males of the genotype I is ambiguous. In the closely related species X. pygmaeus, males are of size similar to smaller X. nigrensis males. Paradoxically, these males do not show the courtship display that typifies larger male X. nigrensis and many other species of swordtails, but instead often employ chase behavior identical to the alternative mating behavior in small male X. nigrensis. We suggest that historical and genetic constraints, in addition to current selection forces, might be important factors in explaining the existence of alternative mating behavior in X. pygmaeus.     

Antennal response to fragrance compounds in male orchid bees

Summary. Male orchid bees (Euglossini) are attracted to floral and non-floral odours, which they collect and accumulate in hind tibial cavities for subsequent exposure during courtship. Fragrance preferences are species-specific, leading to relatively specialised pollination of euglossophilous plants. We tested the hypothesis that preferences for attractive compounds have led to species-specific sensory adaptations that are measurable by electroantennography (EAG). All of 16 synthetic fragrance compounds elicited significant responses on male bee antennae, with some difference of response spectra between individuals of Euglossa spp. and bumblebee (Bombus terrestris) controls, but no difference between three different species of Euglossa. There was no correspondence between a compounds’ attractiveness in baiting assays and the size of its electrophysiological response. Our results strengthen the view that fragrance preferences are largely mediated by processes in higher nervous centres. Peripheral sensory tuning to single attractive odorants may be constrained by the need to detect and discriminate between many fragrances, including many that have repellent effects on male bees.     

Sex change limited by paternal care: a test using four Mediterranean labrid fishes,genus Symphodus

Four species of the Mediterrnean wrasse (genus Symphodus) were investigated under natural conditions near Calvi, Corsica, France, to test the idea that extensive male mating-investment limits the extremes of male reproductive success, and thus reduces selection for protogynous sex change. The four species differ in the extent to which males build nests and care for the eggs, and this sort of paternal care can detract from time spent in mating. In S. ocellatus and S. roissali larger males construct an elaborate nest, ventilate the eggs, and engage in territorial defense. The spawning rates for these males are relatively low and variable due to long periods spent in nest construction and egg tending. They also suffer a large amount of interference from smaller males, which may be due to the predictability of nest location. Sex change appears to be absent. S. tinca males construct only a rudimentary nest, do not ventilate the eggs, and experience much less spawning interference. Large males are relatively more successful in mating in this species, and sex change appears to occasionally occur. The large males of S. melanocercus spawn at a much higher rate than small males, due in part to the fact that they do not construct or defend nests and thus are able to spawn on a daily basis. Sex change appears to be common in this species. Thus, the species that shows the greatest sexual difference in changes of expected fertility with size is also the species that shows the strongest expression of sex change. Studies such as this can begin to indicate the actual costs of changing sex.     

Testing the ability of males and females to respond to altered songs in the dueting green lacewing, Chrysoperla plorabunda (Neuroptera: Chrysopidae)

Green lacewings in the carnea group of Chrysoperla engage in species-specific heterosexual duets using low-frequency substrate-borne signals. Within each species, both sexes sing nearly identical songs. Songs are the principal barriers to hybridization between sympatric species in the complex. Here, we investigated the responsiveness of males and females of Chrysoperla plorabunda to synthesized, prerecorded songs that differed from the species mean in the period between repeated volleys of abdominal vibration. We tested 15–16 males and 15–16 females using playbacks of two signals that gradually increased or decreased in volley period, starting at the species mean. We found that (1) duets during courtship are accurate, interactive, and adjustable by each participant; (2) in staged duets, both sexes respond best to song tempos near the mean volley period of their population, but can nonetheless maintain duets with signals of nearly twice, or half, the normal volley period; (3) individuals fine-tune their adjustments to signals of different volley periods by changing their own volley duration and latent period, or less often by inserting extra volleys or skipping every other volley; (4) males are significantly better at matching signals of changing tempo than females; and (5) the range of song responsiveness of C. plorabunda does not overlap the natural range of volley periods found in Chrysoperla adamsi, an acoustically similar sibling species, thus reaffirming strong behavioral isolation. In sum, the precise, almost unbreakable heterosexual duets characteristic of song species of the carnea group result from tight mutual feedback between partners. Effective reproductive isolation between species can be based on song differences alone.     

Parental care and mate attraction in the Florida flagfish, <Emphasis Type="Italic">Jordanella floridae</Emphasis>

Theory suggests that there is a trade-off between mate attraction and investment in parental care. Yet, under some circumstances, such as in species with uniparental male care, it is conceivable that males who provide more care also attract more females, and hence avoid this cost. We tested these two alternative hypotheses using the Florida flagfish, Jordanella floridae, which is a highly sexually dimorphic species with male parental care. We predicted that if components of male care behavior primarily serve offspring survival, they should display these behaviors more in the presence of eggs than without eggs. We also predicted that males should show a trade-off between display, and other activities directed to other fish, and care behaviors. Alternatively, if care has a positive effect on mating success, we expected males to show care even in the absence of eggs, and that they should display more care in the presence of females. We found that care behavior mostly depended on the presence of eggs, males increased care when they guarded eggs, and there was a negative relationship between rates of interaction and care behavior. Most care was exhibited in the absence of other fish while the presence of males and females both had a negative effect on care behavior. There was no difference in care behavior with males or females present. Only nest-visitation rates were highest in the presence of females, suggesting that this behavior is used as part of the courtship. These results support the idea that male care in this species is primarily influenced by natural selection. Males did, however, display fanning and other egg-directed behaviors even in the absence of eggs. The level of these behaviors was constant and independent of display behavior. Hence, it seems that care may be used in mate attraction before the male has received his first clutches.     

Field presentation of male secretions alters social display in Sceloporus virgatus but not S. undulatus lizards

Lizards have communicative displays involving primarily vision and chemicals, and recent work suggests trade-offs between these two modalities. In reptiles, little work assesses effects of conspecific chemicals on subsequent signaling behavior. Here, we studied responses to conspecific secretions in two Sceloporus species differing in visual signaling: male Sceloporus undulatus have blue abdominal patches used in aggressive territorial encounters, while Sceloporus virgatus males have evolutionarily lost the patches and have low rates of aggressive display. We measured behavior of free-ranging males following presentation of swabs with conspecific male chemicals from femoral glands and the cloaca, or of clean swabs. For male S. undulatus (blue), neither likelihoods nor rates of behavioral responses differed between swab treatments. In contrast, male S. virgatus (white) presented with secretions had significantly higher likelihood of performing head bob, push-up, and shudder displays, than males in control swab trials. Rates of behavior also differed for S. virgatus, with higher rates of push-up display and tongue flick in trials with conspecific chemicals, but rates of other displays, number of moves, and mean total distance moved did not differ between treatments. Male S. undulatus moved significantly greater distances than S. virgatus, independent of treatment. In sum, male S. virgatus responded to conspecific male chemicals by increasing their low rates of display behavior, whereas male S. undulatus did not alter their already high rates of display or movement following chemical exposure. Chemical signals may play a different role in social signaling in the species with the loss of the abdominal color signal.     

Spatio-temporal changes in diversity and community structure of planktonic copepods in Sagami Bay, Japan

Seasonal changes in diversity and community structure of planktonic copepods at a shelf site in Sagami Bay, Japan was studied in relation to cross-shelf interaction of species components. Seasonal mesozooplankton samples were collected from the shelf station (St. M) of the north-west part of Sagami Bay from 1995 to 1997. Vertical multi-layered samples were collected near the center of Sagami Bay (St. P) in June 1996. A total 185 copepod species were identified from the two stations. We observed a clear seasonal succession in calanoid diversity and community structure at St. M from a simple shelf water community (>11 species) during spring blooming periods to highly diverse and mixed communities (ca 20–30 species) of shelf water species coupled with various Kuroshio Current species during late summer to autumn. Cluster and non-metric multidimensional scaling ordination analyses showed two distinct calanoid community groups. One group, which included samples of St. M and the surface layer of St. P, consisted of shelf water species, such as Calanus sinicus, Ctenocalanus vanus, Paracalanus spp., and Kuroshio species, such as, Canthocalanus pauper, Scolecithrix danae, etc. The other cluster was restricted to the samples collected from mid and deep layers at St. P, which consisted of meso- and bathypelagic species and Oyashio species (cold-current species, such as Neocalanus cristatus, Pseudocalanus spp., Eucalanus bungii and Metridia pacifica). In the mid and deep layers at St. P, the population of dormant copepodid stage V (CV) of Eucalanus californicus and C. sinicus were dominant. The deep CV population of C. sinicus might be ecologically discriminated from the surface and shelf water population due to their larger body length and dormant life cycle. E. californicus was also collected at the shelf site during each spring bloom period, whereas the population might descend into the mid- and deep-layers of the central bay before summer. Our results suggest that the seasonal fluctuation of community structure in the shelf water was controlled by both physical (Kuroshio Current) and biological factors, i.e., spring bloom and ontogenetic vertical migration of E. californicus. In particular, transport and diffusion processes of Kuroshio Current in Sagami Bay played a key role in controlling the shelf water calanoid community.     

The use of nondestructive methods to assess a physiological status and conservation perspectives of <Emphasis Type="Italic">Eryngium maritimum</Emphasis> L.

Eryngium maritimum is a perennial species growing exclusively in a coastal littoral zone both on sand dunes and shingle beach and indicated as declining in Northern Europe. The objective of the present study was to prove the use of nondestructive physiological measurement methods to access physiological status of endangered plants, using E. maritimum as a model species. Plants from two Latvian sites were studied in comparison with other populations in Northern Europe (Estonia, Lithuania, Poland, United Kingdom) to find out if local differences in environmental factors affect vitality of E. maritimum individuals. Noninvasive chlorophyll analysis and chlorophyll a fluorescence measurements were used as indicators of plant physiological status through characterization of various aspects of photochemistry of photosystem II activity. Dynamics and morphology of individuals were investigated for evaluation of clonal growth potential of E. maritimum in natural conditions. Highly fluctuating trend of dynamics of individuals (within 40 groups at two Latvian sites) was established for E. maritimum in natural conditions over a five-year period. Disturbance of individuals lead to formation of new shoots from nodal root meristems. An exponential regression between fluorescence parameters F_V/F_M and Performance Index and summary monthly precipitation was found indicating that E. maritimum plants had significant tolerance to water shortage together with susceptibility to increased precipitation. Negative correlation between leaf chlorophyll content and more northern localization of individuals was found (r = 0.95 and r = 0.94, for generative and vegetative shoots, respectively). Northern populations of E. maritimum are endangered by high precipitation in conditions of low air temperature, leading to decrease of photosynthetic productivity and overall physiological status. High developmental plasticity at the root level leads to clonal growth and an efficient survival and relatively long life span of E. maritimum individuals. Chlorophyll a fluorescence is a useful method to search for the effect of suboptimal conditions on physiological status of endangered plant species without elimination and disturbance of individuals.     

Parental investment in two solitary wasps Ancistrocerus adiabatus and Euodynerus foraminatus (Eumenidae: Hymenoptera)

Summary Females of the solitary eumenid wasps Ancistrocerus adiabatus and Euodynerus foraminatus control the adult size of their offspring by the amount of food provded to the larvae. For both species, larger females provision more offspring and collect more food than smaller females. Males of E. foraminatus, upon emergence as adults, fight for control of the nest area. The winning brother remains at the nest and mates with his sisters as they emerge several days later. Males of A. adiabatus are not as agonistic as males of E. foraminatus so that a number of males may remain near the natal nest. When females nest near each other, male-male interactions increase, and the likelihood of sibling mating decreases. Under conditions of clumped nesting, females make larger offspring and invest more in males than when nesting in isolation.     

Non-independent mate choice in a fiddler crab: a case of stimulus enhancement

Non-independent mate selection occurs when the choice behavior of a female is altered by the interactions between other females and males. In the fiddler crab Uca mjoebergi, males court mate-searching females by waving their one greatly enlarged claw. When a female approaches a male, he initiates high-intensity waving. We conducted one natural mate choice experiment and two mate choice experiments using custom-built robotic crabs. We show that the decision of one female to approach a group of males increases the probability that another female will approach and visit a male from the same group. We suggest that this behavior is best explained by the ‘stimulus enhancement’ hypothesis, where the presence of a female near a group of males makes them more likely to be detected by other females due to an increase in male display rate.     

Correlates of male mating success in two species of Anthidium bees (Hymenoptera : Megachilidae)

Summary Field observations were made on the mating behavior of two congeneric species of solitary bees, Anthidium porterae in an arid grassland and A. palliventre in a coastal sand dune habitat. Males of both species exhibited resource defence polygyny and defended hostplants to gain access to females foraging for nectar and pollen. The mating frequencies of marked and measured resident (territorial) males were monitored during periods of continuous observation, following which measurements of territory size and floral resources were obtained. Mating success of A. palliventre males was strongly influenced by territory characteristics: Males that defended small areas with a few rich hostplant patches mated more often than males that held larger territories containing many hostplant patches of low floral density. Large males generally held high-quality sites and thus had a mating advantage over smaller individuals. In A. porterae, on the other hand, male mating success was unrelated to any measure of territory quality. Copulation frequency and male size were positively correlated, however, apparently due to the increased ability of large males to seize and hold females for mating. The two species also differed in the incidence of non-territorial, sneaky males. While absent in A. palliventre, sneaky males accounted for 12% of all mating observed in A. porterae. Males of A. porterae that displayed sneaky tactics mated, on average, as often as resident males. Offprint requests to: E.M. Villalobos     

Intermorph breeding and the potential for reproductive isolation in polymorphic mole salamanders (Ambystoma talpoideum)

The study of reproductive isolation as a prerequisite to sympatric speciation has been limited by the focus on species that have already experienced such isolation. However, a complete understanding of how such processes evolve depends on observing taxa before they complete the speciation process. We studied the potential for sexual isolation in the polyphenic mole salamander, Ambystoma talpoideum, using a series of laboratory and field experiments. This species consists of aquatic paedomorphic adults and terrestrial metamorphic adults which are exhibited by both sexes and which mate in the same aquatic habitat. Previous field studies on this species suggested that intermorph breeding would be less common during the winter months, because paedomorphic adults begin breeding in early autumn and thus may have less energy available for reproduction in the winter. Laboratory experiments conducted during the winter showed that the mating behavior of paedomorphic males occurred at a much lower frequency than that of metamorphic males. In contrast, field experiments that best mimicked natural conditions revealed symmetric intermorph breeding and included multiple paternity shared among males of each morph. This and other studies suggest that there is little evidence of sexual isolation among morphs based on behavioral interactions alone. However, the potential for partial isolation still occurs because of temporal and spatial differences in the frequencies of each morph in nature. Our results suggest that further studies on this system, and other similar polyphenisms, may provide valuable insight into the mechanisms that underlie the evolution of reproductive isolation.     

Digestive mechanics and gluttonous feeding in the feather starOligometra serripinna (Echinodermata: Crinoidea)

The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°3842S; 145°2710E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity.     

Ancient divergences and recent connections in two tropical Atlantic reef fishes<Emphasis Type="Italic"> Epinephelus adscensionis</Emphasis> and<Emphasis Type="Italic"> Rypticus saponaceous</Emphasis> (Percoidei: Serranidae)

Reef habitats of the tropical Atlantic are separated by river outflows and oceanic expanses that may preclude larval dispersal or other population connections in shorefishes. To examine the impact of these habitat discontinuities on the intraspecific phylogeography of reef-associated species we conducted range-wide surveys of two amphi-Atlantic reef fishes that have dispersive pelagic larval stages. Based on 593 bp of mtDNA cytochrome b from the rock hind Epinephelus adscensionis and 682 bp from the greater soapfish Rypticus saponaceous (n=109 and 86, respectively), we found evidence of relatively ancient separations as well as recent surmounting of biogeographic barriers by dispersal or colonization. Rock hind showed slight but significant population genetic differentiation across much of the tropical Atlantic Ocean (_ST=0.056), but deep divergence between the southeastern United States and seven other localities from the Bahamas to the south, central and east Atlantic (mean pairwise d=0.040, overall _ST=0.867). The geographic distribution of the two rock hind lineages is highly unusual in genetic studies of Caribbean Sea reef fishes, because those lineages are separated by less than 250 km of open water within a major biogeographic region. In contrast, highly significant population genetic structure was observed among greater soapfish from the SW Caribbean, Brazil, and mid-Atlantic ridge (_ST=0.372), with a deep evolutionary separation distinguishing putative R. saponaceous from West Africa (mean pairwise d=0.044, overall _ST=0.929). Both species show evidence for a potential connection between the Caribbean and Brazilian provinces. While widespread haplotype sharing in rock hind indicates that larvae of this species cross oceanic expanses of as much as 2000 km, such a situation is difficult to reconcile with the isolation of populations in Florida and the Bahamas separated by only 250 km. These findings indicate that populations of some species in disjunct biogeographic zones may be isolated for long periods, perhaps sufficient for allopatric speciation, but rare gene flow between zones may preclude such evolutionary divergence in other species.Communicated by P.W. Sammarco, Chauvin     

The social and mating systems of two labrid fishes,Halichoeres maculipinna and H. garnoti,off the Caribbean coast of Panama

Large males of both species are territorial, particularly when spawning. Small Halichoeres maculipinna (but not H. garnoti) are territorial towards equal sized conspecifics, but not towards dissimilar sized conspecifics or any individuals of an abundant congener. Territoriality of small H. maculipinna may be related to the process of sex-change rather than defense of food. Both sexes of both species, but particularly H. maculipinna, migrate from feeding areas to spawning sites at the edges of reefs at specific times of day. In the two species a large male spawns both with females that live in his feeding area and with many others. Differences in the mating system of H. maculipinna in Panama and Florida seem related to habitat differences at those sites. The relative spatial distributions of feeding and spawning sites may affect (a) whether a female spawns with a large male with whom she feeds, and (b) the ability of large males to monopolize mates at the expense of small males. The spawning success of small males seems to depend on whether large males can penalize their participation in spawning rather than on the ability of small males to predict the occurrence of (and then interfere in) spawnings by large males. In both species, the male-specific color pattern is most intensely exhibited by large males during sexual interactions and tends to be lost when they are being aggressive towards conspecifics. The evolutionary development of such a color pattern in labroid fishes seems to be a response to intersexual rather than intrasexual interactions.     

Black spots and female association preferences in a sexual/asexual mating complex (Poecilia, Poeciliidae, Teleostei)

We investigated whether female association preferences for males are influenced by black spot disease (BSD), a parasite induced change of the host phenotype. We compared three different species of fish: a gynogenetic hybrid species, Poecilia formosa (amazon molly) and two sexual species (Poecilia latipinna and Poecilia mexicana), which were involved in the natural hybridisation leading to the amazon molly. Contrary to their sexual relatives, asexual amazon mollies significantly avoided images of males infected with black spot disease. We propose that amazon molly females have direct fitness benefits from choosing healthy males. The adaptive significance of the preference for BSD-uninfected males in the asexual amazon molly is yet unclear but may involve avoidance of predation or parasite infection as well as increased sperm availability.