Suite Of Life History Characteristics Research Articles

Male Sexual Trait Decay in Two Asexual Springtail Populations Follows Neutral Mutation Accumulation Theory

The transition to asexual reproduction is frequent and widespread across the tree of life and constitutes a major life history change. Without sexual reproduction, selection on sexually selected traits is expected to be weaker or absent, allowing the decay and ultimately loss of sexual traits. In this study, we applied an experimental approach to investigate the decay of reproductive traits under asexuality in two asexual populations of the springtail Folsomia candida. Specifically, we compared several key male sexual traits of a sexual population and two distinct parthenogenetic lines. To allow direct comparisons between sexual and asexual individuals we first determined a suite of life history characteristics in the sexual F. candida population, which performs an indirect transfer of sperm packages (spermatophores).To investigate the decay of male sexual traits under asexuality we measured the size of spermatophores, quantified the amount of sperm DNA material, and tested spermatophore attractiveness to females in all three populations. The amount of sperm DNA material in the sperm droplets and the attractiveness of spermatophores were lower in the asexual lines compared to the sexual population. However, the two asexual lines differed in the extent of decay of these traits. Our results are consistent with predictions from neutral mutation accumulation theory, and thus suggest this to be the main evolutionary process underlying the decay of male traits in F. candida.

Drivers of predatory behavior and extreme size in house mice Mus musculus on Gough Island

Abstract In comparison to the mainland, populations of rodents on islands are often characterized by a suite of life history characteristics termed the “island syndrome.” Populations of rodents introduced to islands are also well known for their impacts on native species that have evolved in the absence of mammalian predators. We studied the ecology and behavior of introduced house mice Mus musculus on Gough Island where they are the only terrestrial mammal and where their predatory behavior is having a devastating impact on the island’s burrowing petrel (order Procellariiformes ) population and the Critically Endangered Tristan albatross Diomedea dabbenena . Mice on Gough exhibit extreme features of the island syndrome, including: a body mass 50–60% greater than any other island mouse population, peak densities among the highest recorded for island populations, and low seasonal variation in numbers compared to other studied islands. Seasonal patterns of breeding and survival were linked to body condition and mass, and mice in areas with high chick predation rates were able to maintain higher mass and condition during the winter when mouse mortality rates peak. Within-site patterns of chick predation indicate that proximity to neighboring predated nests and nesting densities are important factors in determining the likelihood of predation. We conclude that selection for extreme body mass and predatory behavior of mice result from enhanced overwinter survival. Small mammal populations at temperate and high latitudes are normally limited by high mortality during the winter, but on Gough Island mice avoid that by exploiting the island’s abundant seabird chicks.

Influence of ecology and landscape on snake road mortality in a sagebrush‐steppe ecosystem

AbstractRoads fragment our landscape, posing a severe threat to the persistence of wildlife populations through losses of individuals to direct mortality and decreased connectivity. Although they possess a particular suite of life history characteristics that make them especially vulnerable, snakes tend to be underrepresented in research examining vertebrate road mortality. Here, we report a statistical analysis of snake mortality along a 183‐km road circuit in sagebrush‐steppe habitat located in southeastern Idaho. We describe differential road mortality across snake species, season, sex and age. We also analyze both fine‐scale and broad‐scale habitat measurements to identify various habitat and landscape factors associated with snake road mortality. Our results show clearly that snake road mortality is influenced by interactions among demographic, ecological and temporal factors. Vagile species and life stages were particularly vulnerable to road mortality during periods of peak activity. Gophersnakes dominated our road observations, with adult male mortality peaking in spring and high casualties of neonates in the fall. Snake crossings were especially common along roadsides with high vegetative cover, in areas dominated by non‐native grasses. These results suggest the potential for snake populations to become fragmented over time, and that habitat conversion and species invasions may be compounding this effect. This study suggests that conservation efforts need to account for inter‐ and intraspecific differences in road mortality risk and provides guidance for roadside management that may serve to minimize vertebrate mortality on roads.

Biology of extinction risk in marine fishes

We review interactions between extrinsic threats to marine fishes and intrinsic aspects of their biology that determine how populations and species respond to those threats. Information is available on the status of less than 5% of the world's approximately 15500 marine fish species, most of which are of commercial importance. By 2001, based on data from 98 North Atlantic and northeast Pacific populations, marine fishes had declined by a median 65% in breeding biomass from known historic levels; 28 populations had declined by more than 80%. Most of these declines would be sufficient to warrant a status of threatened with extinction under international threat criteria. However, this interpretation is highly controversial, in part because of a perception that marine fishes have a suite of life history characteristics, including high fecundity and large geographical ranges, which might confer greater resilience than that shown by terrestrial vertebrates. We review 15 comparative analyses that have tested for these and other life history correlates of vulnerability in marine fishes. The empirical evidence suggests that large body size and late maturity are the best predictors of vulnerability to fishing, regardless of whether differences among taxa in fishing mortality are controlled; there is no evidence that high fecundity confers increased resilience. The evidence reviewed here is of direct relevance to the diverse criteria used at global and national levels by various bodies to assess threat status of fishes. Simple life history traits can be incorporated directly into quantitative assessment criteria, or used to modify the conclusions of quantitative assessments, or used as preliminary screening criteria for assessment of the approximately 95% of marine fish species whose status has yet to be evaluated either by conservationists or fisheries scientists.

Lotic meiofaunal community dynamics: colonisation, resilience and persistence in a spatially and temporally heterogeneous environment

1. The spatial and temporal dynamics of lotic meiofaunal communities were examined with a focus on colonisation, maintenance of populations in lotic environments and persistence of meiofaunal communities.2. Lotic meiofaunal colonisation of new habitats may take place via a number of mechanisms and is rapid at both the patch scale (within hours–days) and the drainage basin scale (within 20 years). Successional patterns in lotic meiofaunal communities are evident although data are extremely limited.3. Lotic meiofaunal communities appear to be resilient to high flow disturbances. Resilience is moderated by the availability of in‐stream refugia and habitat hydrology. Lotic meiofauna may also adopt a ‘refuge as habitat‘ approach to such disturbances.4. Lotic cyclopoid copepods possess a common suite of life history characteristics that confers resilience to disturbances. Compared to pelagic planktonic species they have short generation times, many descendants per reproductive cycle and long lifespans. Females in ‘source‘ populations are likely to survive disturbances and so could continuously reproduce over a long period of time producing large numbers of offspring which develop rapidly and recolonise ‘sink‘ areas of the stream.5. Persistence of lotic meiofaunal communities is highly variable. Meiofaunal persistence does not increase with increasing proportions of in‐stream flow refugia.

Reproduction in the Rattlesnake, Sistrurus miliarius barbouri, in Central Florida

Reproduction in the Rattlesnake, Sistrurus miliarius barbouri, in Central Florida

Comparisons of Allozyme Diversity Among Rare and Widespread Rhus Species

Genetic diversity in three species of Rhus was investigated using starch gel electro- phoresis. Rhus michauxii is a rare species endemic to North Carolina, whereas R. glabra and R. copallina are widespread. All three species are clonal, typically dioecious, woody shrubs. Forty-seven percent of the loci examined for R. michauxii were polymorphic, compared to 88% of the loci examined for both R. glabra and R. copallina. Mean genetic diversity (He) within populations of R. michauxii (0.05) was lower than the genetic diversity within populations of R. glabra and R. copallina (0.15 for both species). Mean number of multilocus genotypes per population was lower for R. michauxii, 4.1, versus the other two species, R. glabra, 27.5 and R. copallina, 26.6. Genotypic diversity indices (DG) were 0.41, 0.95 and 0.95 for R. michauxii, R. glabra and R. copallina, respectively. The proportion of genetic diversity among populations (GST) was higher in R. michauxii (0.335) and R. copallina (0.301) than in R. glabra (0.198). Genetic identity values among the species ranged from 0.52-0.96, and grouped R. michauxii closely with R. glabra. Rhus glabra and R. copallina have levels of genetic diversity similar to wide ranging plant species with the same suite of life history characteristics. The lower level of genetic diversity in R. michauxii is characteristic of species with limited geographic distributions. The relatively high levels of genetic diversity seen among populations indicates that clonal repro- duction may play an important role in the genetic structuring of these species.