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11.
The Botanist Effect Revisited: Plant Species Richness, County Area, and Human Population Size in the United States 总被引:3,自引:0,他引:3
Abstract: The "botanist effect" is thought to be the reason for higher plant species richness in areas where botanists are disproportionately present as an artefactual consequence of a more thorough sampling. We examined whether this was the case for U.S. counties. We collated the number of species of vascular plants, human population size, and the area of U.S. counties. Controlling for spatial autocorrelation and county area, plant species richness increased with human population size and density in counties with and without universities and/or botanical gardens, with no significant differences in the relation between the two subsets. This is consistent with previous findings and further evidence of a broad-scale positive correlation between species richness and human population presence, which has important consequences for the experience of nature by inhabitants of densely populated regions. Combined with the many reports of a negative correlation between the two variables at a local scale, the positive relation between plant species richness in U.S. counties and human population presence stresses the need for the conservation of seminatural areas in urbanized ecosystems and for the containment of urban and suburban sprawl. 相似文献
12.
A total of 250 nestboxes were arranged in five plots in a suburban area of Budapest, Hungary (19°04E, 47°41N). In each plot, 25 were placed at 50 m intervals to simulate solitary breeding and 25 3–5 m apart to simulate colonial breeding. Length of nest building period, feeding frequency, nestling mortality, nestlings' diet, productivity and parental condition were compared for colonial and solitary breeding tree sparrows Passer montanus. Parents with long nest-building periods, including the majority of first-year females, produced fewer young than parents which built over short periods. Parents fed nestlings morefrequently and nestlings had lower mortality in second than first broods; whether or not a third brood was reared was determined by the costs invested in first and second broods. Females that laid a third clutch had reared fewer young in first and second broods and were heavier than females that reared many young in two broods. Colonial birds had higher feeding frequencies, more similar diets and suffered lower nestling mortality than solitary parents for first broods, but they fed less frequently, diets were less similar, and nestling mortality was higher in second and third broods. It is suggested that colonial breeders benefited from the social stimulation of simultaneous feeding in first broods, but the advantage of synchronicity in feeding declined in second broods and the sparser breeding spacing of solitary parents was more advantageous for feeding in second and third broods. Birds that changed nest spacing between broods had fed nestlings less frequently and had higher nestling mortality before changing than birds which retained their spacing. Parents which changed from colonies to solitary nests fed more frequently with lower nestling mortality in the next brood than parents which retained colonial nests for their second (and third) brood. Solitary parents did not show such a relationship. The rearing of three broods caused higher weight loss in colonial than solitary parents.Correspondence to: L. Sasvári 相似文献
13.
William D. Brown 《Behavioral ecology and sociobiology》1993,33(3):151-157
Summary Examples of positive assortative mating by body size are abundant but its causes remain controversial. I show that size-assortative mating occurs in the chrysomelid beetle Trirhabda canadensis and I test a series of alternative hypotheses to explain how this mating pattern comes about. Results suggest that assortative mating in this beetle is due to the greater ease with which size-matched pairs can achieve intromission, and not due to size-biased skews in the availability of mates or mate choice favoring large individuals. There was no correlation between male and female elytron length (a measure of body size) at the initiation of courtship, but pairs assorted positively by size at the onset of intromission. Moreover, in the laboratory, there was a negative correlation between male and female size for pairs engaged in courtship that terminated without mating. Assortative mating was not associated with a large-male mating advantage and there was no evidence of female choice of large males. Nor was there unequivocal evidence for male choice of large females; although mating females were slightly larger and considerably heavier than solitary females, males did not differ in the frequency with which they rejected large and small females. Assortative mating in T. canadensis appeared to be caused by the lower ability of mismatched pairs to achieve intromission after an encounter, both when males were larger and when they were smaller than the female. 相似文献
14.
Akiko Matsumoto-Oda Miya Hamai Hitosige Hayaki Kazuhiko Hosaka Kevin D. Hunt Eiiti Kasuya Kenji Kawanaka John C. Mitani Hiroyuki Takasaki Yukio Takahata 《Behavioral ecology and sociobiology》2007,61(5):661-668
Although estrous synchrony has been reported in a number of mammalian species, most often among primates, methodological and
analytical problems make it difficult to interpret these results. We developed a novel estrous synchrony index and employed
a randomization procedure to analyze long-term observations of female chimpanzee (Pan troglodytes schweinfurthii) estrous cycles at the Mahale Mountains National Park, Tanzania. Our results revealed that female chimpanzees at Mahale avoid
synchronizing their estrous periods with each other. We also found that birthrates decreased as the breeding sex ratio increased.
We suggest that estrous asynchrony decreases female–female competition for mates. Asynchrony may also reduce the potential
for male sexual coercion by nonpreferred mating partners. 相似文献
15.
Experimental and natural changes in the peacock's (Pavo cristatus) train can affect mating success 总被引:4,自引:0,他引:4
Petrie et al. (1991) demonstrated a correlation between the degree of elaboration of peacocks' trains and their mating success, and also showed that this correlation occurred because females preferred to mate with the male that had the most elaborate train of those sampled on the lek. Although these data suggest that female choice is responsible for non-random mating in this species, they do not conclusively show that train morphology is the cue that females respond to, because they do not rule out the possible influence of another unidentified variable which is correlated with train elaboration. This paper presents an experimental test of the importance of the peacock's train in determining male mating success. If the number or arrangement of eye-spots in the peacock's train influences mating success, then changing the number of eye-spots should change mating success. This prediction was tested in an experiment where the trains of male peafowl (Pavo cristatus) were manipulated by removing a number of eye-spots between mating seasons. Peacocks with eye-spots removed showed a significant decline in mating success between seasons compared with a control group. This result, together with the observational data, supports the hypothesis that the peacock's train has evolved, at least in part, as a result of female choice. 相似文献
16.
Véronique Thériault Louis Bernatchez Julian J. Dodson 《Behavioral ecology and sociobiology》2007,62(1):51-65
Salmonids are known for the occurrence in sympatry of two life-history forms, one that undergoes migration to sea before returning
to freshwater to reproduce (anadromous) and one that inhabits freshwater without a migration phase (resident). Whereas one
breeding population is often suggested by population genetic studies, mating patterns have rarely been directly assessed,
especially when both sexes are found within each life-history form. By using highly polymorphic microsatellite loci and parentage
analysis in a natural population of sympatric anadromous and resident brook charr (Salvelinus fontinalis), we found that gene flow occurred between the two forms and was mediated by resident males mating with both resident and
anadromous females. Determinants of reproductive success, estimated by the number of surviving juveniles (ages 1 and 2 years),
differed between the sexes. No strong evidence of the influence of size on individual reproductive success was found for males,
whereas larger females (and hence most likely to be anadromous) were more successful. The higher individual reproductive success
of anadromous fish compared to residents was mainly explained by this higher reproductive success of anadromous females. We
suggest that resident males adopt a “sneaking” reproductive tactic as a way of increasing their reproductive success by mating
with females of all sizes in all habitats. The persistence of the resident tactic among females may be linked to their advantage
in accessing spatially constrained spawning areas in small tributary streams unavailable to larger females. 相似文献
17.
Gita R. Kolluru Gregory F. Grether Heidy Contreras 《Behavioral ecology and sociobiology》2007,61(5):689-701
Food availability is expected to influence the relative cost of different mating tactics, but little attention has been paid
to this potential source of adaptive geographic variation in behavior. Associations between the frequency of different mating
tactics and resource availability could arise because tactic use responds directly to food intake (phenotypic plasticity),
because populations exposed to different average levels of food availability have diverged genetically in tactic use, or both.
Different populations of guppies (Poecilia reticulata) in Trinidad experience different average levels of food availability. We combined field observations with laboratory “common
garden” and diet experiments to examine how this environmental gradient has influenced the evolution of male mating tactics.
Three independent components of variation in male behavior were found in the field: courtship versus foraging, dominance interactions,
and interference competition versus searching for mates. Compared with low-food-availability sites, males at high-food-availability
sites devoted more effort to interference competition. This difference disappeared in the common garden experiment, which
suggests that it was caused by phenotypic plasticity and not genetic divergence. In the diet experiment, interference competition
was more frequent and intense among males raised on the greater of two food levels, but this was only true for fish descended
from sites with low food availability. Thus, the association between interference competition and food availability in the
field can be attributed to a genetically variable norm of reaction. Genetically variable norms of reaction with respect to
food intake were found for the other two behavioral components as well and are discussed in relation to the patterns observed
in the field. Our results indicate that food availability gradients are an important, albeit complex, source of geographic
variation in male mating strategies. 相似文献
18.
Independence, not conflict, characterizes dart-shooting and sperm exchange in a hermaphroditic snail
Although the sexes are united in hermaphrodites, conflict can still occur because the male and female functions have separate
interests. We examined the evidence for conflict in the mating system of the terrestrial snail Cantareus aspersus (formerly Helix aspersa) where sharp, calcareous darts are ‘shot’ during courtship. We predicted that the use of the dart would either reflect or
create conflict and this would be evident in either the courtship behavior or the transference of sperm. Previous studies
demonstrated that the dart functions after sperm transfer to increase sperm survival. Using detailed observations of mating
snails, we examined the factors that determine dart shooting order, the behavioral responses after being hit by a dart, the
accuracy of dart shooting, and the allocation of sperm resources. We found that each dart was shot independently, and each
animal appeared to be interested only in getting off the best possible shot, probably one that penetrates deeply near the
genital pore. There is no evidence of mating conflict. Every snail transfers sperm to its partner, and the size of the donation
does not depend on the success or failure of either snail’s dart shot. Although the receipt of a dart does not appear to cause
harm, it may produce indirect costs due to the partial loss of control over fertilization. We conclude that mating in C. aspersus is a partnership in which independent actors demonstrate unconditional reciprocity during courtship and sperm transfer. 相似文献
19.
Abstract: Hunting in tropical forests is typically most intense near human settlements, and this creates gradients of decreasing animal densities toward those settlements. Within the context of this spatial pattern, we evaluated the status of game in the hunting grounds of an indigenous community in eastern Ecuador. We constructed a spatially explicit model of hunter-prey interactions that mimicked the hunting in the village and included realistic animal-dispersal rules. We compared predictions from the model with distributions of animal harvest rates and catch per unit effort of 12 game species. Six species were overharvested in part or all of the area, and two other species were probably being overharvested, although high dispersal rates complicated the interpretation. We then compared our method with methods that have been used previously. We argue that because our method provides information about the spatial extent of overharvesting, it could be particularly useful in informing decision makers about where to establish no-take areas and could therefore aid in improving the sustainability of hunting in tropical forests. 相似文献
20.
Sperm economy and limitation in spiny lobsters 总被引:5,自引:0,他引:5
Sperm limitation, when female fertilisation success is constrained by the supply of sperm, is generally perceived to be an
uncommon feature of reproduction in species which directly transfer gametes during copulation. Male size, previous copulations,
and the balance of expected reproductive return and future mating opportunity may, however, limit the amount of sperm males
transfer to females. We used laboratory experiments where mate size could be manipulated and its consequences on spermatophore
size and clutch size determined, to show that in two genera of spiny lobsters (Crustacea: Palinuridae) male reproductive output
limits the size of clutches brooded by females. In Panulirus argus from the Florida Keys, we show that while male size affects spermatophore area, males also vary the amount of ejaculate positively
with female size. Furthermore, the area of the spermatophore has a greater influence than female size on subsequent clutch
weight. In Jasus edwardsii from New Zealand, female size, male size and mate order all affect clutch weight. In both species, clutches fertilised by
small males in the laboratory are significantly smaller than clutches fertilised by large males. These results suggest that
to ensure they receive sufficient sperm, females should either mate several times prior to oviposition, mate as early as possible
in the reproductive season, or choose large, preferably unmated males as partners and thus compete with other females for
preferred males. Sperm-limited female fecundity has the potential to limit the egg production of fished populations where
large males are typically rare.
Received: 18 May 1998 / Received in revised form: 20 November 1998 / Accepted: 30 November 1998 相似文献