Visual Implant Elastomer Mark Retention Through Metamorphosis in Amphibian Larvae

Abstract: Questions in population ecology require the study of marked animals, and marks are assumed to be permanent and not overlooked by observers. I evaluated retention through metamorphosis of visual implant elastomer marks in larval salamanders and frogs and assessed error in observer identification of these marks. I found 1) individual marks were not retained in larval wood frogs (Rana sylvatica), whereas only small marks were likely to be retained in larval salamanders (Eurycea bislineata), and 2) observers did not always correctly identify marked animals. Evaluating the assumptions of marking protocols is important in the design phase of a study so that correct inference can be made about the population processes of interest. This guidance should be generally useful to the design of mark-recapture studies, with particular application to studies of larval amphibians.     

Sea‐level changes and palaeo‐ranges: reconstruction of ancient shorelines and river drainages and the phylogeography of the Australian land crayfish Engaeus sericatus Clark (Decapoda: Parastacidae)

Historical sea levels have been influential in shaping the phylogeography of freshwater‐limited taxa via palaeodrainage and palaeoshoreline connections. In this study, we demonstrate an approach to phylogeographic analysis incorporating historical sea‐level information in a nested clade phylogeographic analysis (NCPA) framework, using burrowing freshwater crayfish as the model organism. Our study area focuses on the Bass Strait region of southeastern Australia, which is marine region encompassing a shallow seabed that has emerged as a land bridge during glacial cycles connecting mainland Australia and Tasmania. Bathymetric data were analysed using Geographical Information Systems (GIS) to delineate a palaeodrainage model when the palaeocoastline was 150 m below present‐day sea level. Such sea levels occurred at least twice in the past 500 000 years, perhaps more often or of larger magnitude within the last 10 million years, linking Victoria and Tasmania. Inter‐locality distance measures confined to the palaeodrainage network were incorporated into an NCPA of crayfish (Engaeus sericatus Clark 1936) mitochondrial 16S rDNA haplotypes. The results were then compared to NCPAs using present‐day river drainages and traditional great‐circle distance measures. NCPA inferences were cross‐examined using frequentist and Bayesian procedures in the context of geomorphological and historical sea‐level data. We found distribution of present‐day genetic variation in E. sericatus to be partly explained not only by connectivity through palaeodrainages but also via present‐day drainages or overland (great circle) routes. We recommend that future studies consider all three of these distance measures, especially for studies of coastally distributed species.     

Parallel divergence of sympatric genetic and body size forms of Arctic charr,Salvelinus alpinus,from two Scottish lakes

F _ST and R_ST estimates for Arctic charr from six microsatelite markers collected from two neighbouring Scottish lakes, Loch Maree and Loch Stack, confirm the presence of two distinct genetic groupings representing separate populations within each lake. In both lakes, there was also a clear body size dimorphism, with large and small body size forms that segregated according to genetic grouping. There was evidence of only subtle foraging ecology differences between morphs, with the small body size morph in both lakes being more generalist in its foraging in the summer (consuming mostly plankton but also some macrobenthos) than the large body size morph, which specialized on planktonic prey. Trophic morphology (head and mouth shape) did not differ significantly between morphs (although the small sample size for Maree makes this a preliminary finding). Cluster analysis of the microsatelite data and the presence of private alleles showed that morphologically similar forms in different lakes were not genetically similar, as would be expected under a multiple invasion hypothesis. Thus, the data do not support a hypothesis of a dual invasion of both lakes by two common ancestors but instead suggest an independent origin of the two forms in each lake. Thus parallel sympatric divergence as a result of common selection pressures in both lakes is the most parsimonious explanation of the evolutionary origin of these polymorphisms. © 2008 The Linnean Society of London, Biological Journal of the Linnean Society, 2008, 95 , 748–757.     

Habitat selection of feral cats (Felis catus) on a temperate,forested island

Abstract Habitat selection of mammalian predators is known to be influenced by availability and distribution of prey. The habitat selection of feral cats on Stewart Island, southern New Zealand, was investigated using telemetry of radio‐tagged cats. Compositional analysis of the habitat selection of radio‐tagged cats showed they were using the available habitats non‐randomly. Feral cats avoided subalpine shrubland and preferentially selected podocarp‐broadleaf forest. The avoidance of subalpine shrubland by cats was probably due to a combination of the presence of a large aggressive prey species, Norway rats Rattus norvegicus, and the lack of rain‐impervious shelter there. Most cats also used subalpine shrubland more often in dry weather than in wet weather. Cats did not preferentially select all the other habitats with only smaller rat species, Rattus rattus and Rattus exulans, present however. Cats were probably further influenced by the availability of large trees, in podocarp‐broadleaf forest, that can provide shelter. Cats were also more active in dry rather than wet weather which supports this conclusion. Home ranges of feral cats on Stewart Island were some of the largest recorded, probably because of limited primary and alternative prey.     

Life‐history and ecological correlates of decline and extinction in the endemic Australian frog fauna

Abstract Frog populations are rapidly disappearing throughout the world. An important issue for ecologists to resolve is why some frog species are more susceptible to decline than others. Here, we performed a comparative study of the endemic Australian frog fauna to determine whether the life history and ecology of declining species have predisposed them to extinction. Decline was consistently found to be correlated with geographical range size across contemporary species and in analyses based on phylogenetically independent contrasts (PICs). Species with narrow geographical ranges have been disproportionately more susceptible to decline. Across species, decline was also correlated with large body size and a high proportion of the geographical range overlapping with the distribution of cane toads and landscape stress (e.g. land clearing). We show that with the exception of range size, however, correlates of decline across species are underpinned by a small number of evolutionary events. Hence, the suite of traits that correlate with decline in the cross‐species analysis is only relevant to a small number of clades. We also found that clutch size, testes mass, ova size and distributional overlap with feral pigs were not significantly related to decline. In the ongoing search for life‐history and ecological correlates of decline and extinction, our results highlight the importance of performing analyses across contemporary species and using PICs.     

加拉帕戈斯群岛同域达尔文雀种群的进化动态

本文主要论述物种形成的三个阶段 :建群、线形分异和生殖隔离。首先介绍一项通过时间产生分异的调查 ,然后检测种群间基因交流的障碍 ,最后描述一个自然事件从而分析建群过程。本项工作是在加拉帕戈斯群岛中的达芬梅杰岛上长期研究达尔文雀进化工作的一部分 ,研究组成员由格兰特、笔者和其他同事组成。岛上发生适应辐射的时间并不长 ,现存的 1 4种达尔文雀由 2 0 0或 3 0 0万年前的一个祖先分化而成。极端的年间气候波动改变了达尔文雀的生态条件和食物供给。达尔文雀种群受到这些变化的影响 ,通过重复的进化反应 ,发生了自然选择。通过 3 0年的积累 ,中地雀 (Ｇｅｏｓｐｉｚａｆｏｒｔｉｓ)和仙人掌地雀 (Ｇ .ｓｃａｎｄｅｎｓ)种群的体型大小和喙部形状发生了显著的变化。达尔文雀的鸣叫是在幼鸟时期通过学习而形成的 ,类似于印痕过程 ,鸣叫对保持种间的生殖隔离起着一定的作用。但是在一些特殊的生态条件下 ,生殖隔离可以被由于错误印痕所形成的鸣叫而冲破 ,导致种间杂交和基因渗入 ,当然 ,这种情况非常罕见。自然选择可以使基因流从一个物种流动到另一个物种从而增加变异。 1 983年 ,大地雀 (Ｇ .ｍａｇｎｉｒｏｓｔｒｉｓ)在达芬梅杰岛上建群。最初岛上只有拥有共同亲鸟的 2只雄鸟和 1只雌鸟通过不