Integrative Studies of Amphibians: From Molecules to Mating

SYNOPSIS. Studies of reproductive behavior in amphibians havebeen especially successful in synthesizing data produced frommolecular and physiological research with evolutionary parameters,such as measures of reproductive success. In particular, tworelatively new areas of amphibian research are highly amenableto synthetic studies. One area is the nature of chemical communicationby pheromone delivery in terrestrial salamanders. Male courtshippheromones, for example, are delivered to the female duringmating. These pheromones typically are received by the accessoryolfactory system and act (presumably via the hypothalamus) toincrease female receptivity. At an evolutionary level, pheromonedelivery can increase male courtship success and thus the likelihoodthat a given male will sire offspring. Variation in pheromonecomposition and effectiveness will permit us to trace the evolutionof the male pheromone on a phylogeny of related populationsand species. At a proximal level, salamander courtship pheromonesare being chemically analyzed in order to identify specificprotein components that affect female receptivity. It also willbe possible to determine whether chemical variation among malesis related to behavioral effectiveness. Thus, courtship pheromonedelivery is a behavior that has invited scrutiny from a combinationof evolutionary and mechanistic perspectives. The second researcharea that is gaining from a synthetic approach is the investigationof relationships between hormonal mechanisms and reproductivebehavior in field populations of anurans and salamanders. Amphibiansare an understudied group, and the area of hormone-behaviorrelationships is inspired by testable hypotheses based on studiesof other terrestrial vertebrates. The ability to correlate physiologicalmeasures with estimates of reproductive success identifies areasof amphibian research that will profit from continued attention.     

Strategies to protect biological diversity and the evolutionary processes that sustain it

Conservation planning has tended to focus more on pattern (representation) than process (persistence) and, for the former, has emphasized species and ecosystem or community diversity over genetic diversity. Here I consider how best to incorporate knowledge of evolutionary processes and the distribution of genetic diversity into conservation planning and priority setting for populations within species and for biogeographic areas within regions. Separation of genetic diversity into two dimensions, one concerned with adaptive variation and the other with neutral divergence caused by isolation, highlights different evolutionary processes and suggests alternative strategies for conservation. Planning for both species and areas should emphasize protection of historically isolated lineages (Evolutionarily Significant Units) because these cannot be recovered. By contrast, adaptive features may best be protected by maintaining the context for selection, heterogeneous landscapes, and viable populations, rather than protecting specific phenotypes. A useful strategy may be to (1) identify areas that are important to represent species and (vicariant) genetic diversity and (2) maximize within these areas the protection of contiguous environmental gradients across which selection and migration can interact to maintain population viability and (adaptive) genetic diversity. These concepts are illustrated with recent results from analysis of a rainforest fauna from northeast Australia.     

Effects of past climate on Passiflora actinia (Passifloraceae) populations and insights into future species management in the Brazilian Atlantic forest

The Brazilian Atlantic Rainforest is one of the most diverse and threatened ecoregions on the planet and displays high levels of endemism. Despite several population analyses and phylogeographical studies, the origins of its species richness and the evolutionary processes that gave rise to this diversification remain poorly understood, especially at the southern edge of the Atlantic Forest. Passiflora actinia is an indigenous species from the southern Atlantic Forest and, as such, was influenced by climatic changes during the Pleistocene. In this study, we investigated the effects of past climate changes on the genetic diversity of P. actinia, using nuclear and plastid markers. We subsequently suggest strategies for the preservation of this species in particular and the whole ecoregion in general. We employed phylogeographical methods and combined these results with past, present and future ensemble niche models. Genetic variability in P. actinia was similar to that of other species with similar geographical distributions, and geographical structuring was not observed based on either type of genetic marker. Diversification in P. actinia was dated to the Pleistocene, suggesting that climate changes could have influenced the distribution of genetic diversity in this species. Our results predicted that suitable P. actinia habitat will persist in the highlands but will be reduced in the lowlands, especially with higher greenhouse gas concentrations. Conservation efforts should focus on populations with unique genetic units and populations from areas with greater climatic instability. Habitat loss due to deforestation in the Atlantic Forest constitutes a major risk to this species, especially to small populations or those with low diversity indices.     

Environmental stress and adaptational responses: consequences for human health outcomes

With the dramatic pace of modernization of the world's population, human adaptation as a theoretical construct and paradigm will likely become a focal scientific issue involving scientists from many disciplinary areas during the 21st Century. Macro and micro environments are in rapid flux and human populations are exposed to rapid change. The concept of adaptation, at least in the field of biological anthropology and human biology, will likely remain tied to evolutionary processes and concepts of selection and fitness. In this paper, we discuss the theoretical constructs of adaptation and adaptability and select three current examples from our ongoing research that involve studies of adaptation and evolutionary processes in modernizing populations in different locations worldwide.     

分子系统地理学及其应用

分子系统地理学是20世纪70年代中期伴随着对线粒体DNA的认识而开始酝酿发展的,本文回顾了该学科自诞生以来的发展简史,阐述了其研究内容,着重从3个方面介绍了该领域在其它相关学科中的研究进展,总结了该学科存在的问题,并提出重点应解决的3个问题：1）将细胞器基因与遗传信息更为丰富的核基因相结合;2）合生理论在非平衡种群中的发展应用;3）提高对分化时间估计的精确性。     

A stochastic model for integrating changes in species richness and community similarity across spatial scales

Human activities have elevated the extinction of natural populations as well as the invasion of new areas by non-native species. These dual processes of invasion and extinction may change the richness and similarity of communities, but the form these changes take is likely to depend on the manner in which invasions and extinctions occur and the spatial scale at which the changes are measured. Here, we explore the influence of differing patterns of extinction and invasion on the similarity and richness of a meta-community. In particular, we model simple stochastic processes analogous to realistic modes of human-mediated introduction of non-native species and range expansion by native species. We show that different modes of invasion and extinction can produce very different changes in diversity, and that the relative magnitude of these changes depends both on where in the meta-community diversity is measured and the degree of initial species aggregation. At any spatial scale of measurement, changes in the richness and similarity of communities following invasion and extinction are not necessarily strongly coupled: relatively large increases in richness may or may not also be associated with relatively large increases in similarity among communities. Thus, in real systems, the influence of human-induced invasions and extinctions on diversity will depend on both the precise mode of these processes (especially invasion), and how species populations are distributed across space.     

Consequences of range contractions and range shifts on molecular diversity

Due to past and current climatic changes, range contractions and range shifts are essential stages in the history of a species. However, unlike range expansions, the molecular consequences of these processes have been little investigated. In order to fill this gap, we simulated patterns of molecular diversity within and between populations for various types of range contractions and range shifts. We show that range contractions tend to decrease genetic diversity as compared with population with stable ranges but quite counterintuitively fast range contractions preserve higher levels of diversity and induce lower levels of genetic differentiation among refuge areas than slow contractions. Contrastingly, fast range shifts lead to lower levels of diversity than slow range shifts. At odds with our expectations, we find that species actively migrating toward refuge areas can only preserve higher levels of diversity in refugia if the contraction is rapid. Under slow range contraction or slow range shift, active migration toward refugia lead to a larger loss of diversity as compared with scenarios with isotropic migration and may thus not be a good evolutionary strategy. These results suggest that the levels of diversity preserved after a climate change both within and between refuge areas will not only depend on the dispersal abilities of a species but also on the speed of the change. It also implies that a given episode of climatic change will impact differently species with different generation times.     

Developmental variability and the limits of adaptation: Interactions with stress

1. Little evolutionary change may occur at species borders since the cost of accommodating environmental stresses is high. Extreme examples of such stasis include cave animals in stable stressed environments and ‘living fossils’ in widely fluctuating stressed environments. 2. Variability from the molecular to the organismic level tends to be high under extreme stress. At the developmental level, the fitness of such variants may be low. This means that much developmental variability in natural populations may have little evolutionary significance. 3. Rapid evolutionary change of morphological traits is most likely to be based upon genes acting late in a developmental pathway under conditions which are ecologically and energetically permissive. 4. Although some increases in resistance to temperature extremes have been recorded in laboratory selection experiments, major extensions of extremes in natural populations appear difficult to achieve. The energetic costs of surviving extremes at species borders implies that the evolution of major developmental and morphological shifts is more likely to be a feature of populations of more equable habitats.     

Population genetic structure of the striped silverside, Atherinomorus endrachtensis (Atherinidae, Atheriniformes, Teleostei), inhabiting marine lakes and adjacent lagoons in Palau: marine lakes are "Islands" for marine species

Although evidence for the evolution of terrestrial species on islands continues to rapidly accumulate, little is known about the evolution of marine species in geographically isolated environments such as islands as ocean currents often facilitate gene flow among populations. In this study, we focused on marine lakes of the Palau Islands, which are considered to be true analogues of terrestrial islands for marine species. To examine evolutionary processes in marine lakes, we conducted population genetic analyses on marine lake and lagoon populations of the striped silverside, Atherinomorus endrachtensis, using two mitochondrial DNA markers differing in evolutionary rate, the cytochrome b gene and the control region. The analyses revealed that the amount of genetic diversity of marine lake populations is much lower than that of lagoon populations and high levels of genetic differentiation occur among marine lake and lagoon populations. The present study has shown that marine lake populations have been completely isolated and have differentiated from lagoon populations, and each marine lake population is experiencing different evolutionary processes. These findings clearly demonstrate that marine lakes are excellent environments for the evolutionary study of marine species.     

Genomic pattern of adaptive divergence in Arabidopsis halleri, a model species for tolerance to heavy metal

Pollution by heavy metals is one of the strongest environmental constraints in human-altered environments that only a handful of species can cope with. Identifying the genes conferring to those species the ability to grow in polluted areas is a first step towards a global understanding of the evolutionary processes involved and will eventually improve phytoremediation practices. We used a genome-scan approach to detect loci under divergent selection among four populations of Arabidopsis halleri growing on either polluted or nonpolluted habitats. Based on a high density of amplified fragment length polymorphism (AFLP) markers (820 AFLP markers, i.e. ~1 marker per 0.3 Mb), evidence for selection was found for some markers in every sampled population. Four loci departed from neutrality in both metallicolous populations and thus constitute high-quality candidates for general adaptation to pollution. Interestingly, some candidates differed between the two metallicolous populations, suggesting the possibility that different loci may be involved in adaptation in the different metallicolous populations.     

Genetic differentiation among populations of marine algae

Most of the information for genetic differentiation among populations of marine algae is from studies on ecotypic variation. Physiological ecotypes have been described for individuals showing different responses to temperature and salinity conditions. Morphological ecotypes have also been found associated with areas differing in wave exposure or different intertidal positions. Little is known on how genetic variation is organized within and between populations of marine algae. The occurrence of ecotypic variation in some species is evidence for genetic differentiation among populations resulting from selection by the local environment. The rate of dispersal and subsequent gene flow will also affect the level of differentiation among populations. In species with low dispersal, differentiation can arise through chance founder events or random genetic drift. The few studies available have shown that species of algae exhibit a range of dispersal capabilities. This information can be useful for predicting the potential level of genetic differentiation among populations of these species. Crossing experiments with several species of algae have shown that populations separated by a considerable distance can be interfertile. In some cases individuals from these populations have been found to be morphologically distinct. Crosses have been used to study the genetic basis of this variation and are evidence for genetic differentiation among the populations sampled. Genetic variation of enzyme proteins detected by electrophoresis provides an additional method for measuring genetic variation within and between populations of marine algae. Electrophoretic methods have previously been used to study systematic problems in algae. However, there have been few attempts to use electrophoretic variation to study the genetic structure of populations of marine algae. This approach is outlined and includes some of the potential problems associated with interpreting electrophoretic data. Studies of electrophoretic variation in natural populations ofEnteromorpha linza from Long island Sound are used as an example. This species was found to reproduce only asexually. Despite a dispersing spore stage, genetic differentiation was found on a microgeographic scale and was correlated with differences in the local environment of some of the populations. Similar studies on other species, and especially sexually reproducing species, will add to a growing understanding of the evolutionary genetics of marine algae.Paper presented at the Seaweed Biogeography Workshop of the International Working Group on Seaweed Biogeography, held from 3–7 April 1984 at the Department of Marine Biology, Rijksuniversiteit Groningen (The Netherlands). Convenor: C. van den Hoek.     

Towards a new evolutionary synthesis

New concepts and information from molecular developmental biology, systematics, geology and the fossil record of all groups of organisms, need to be integrated into an expanded evolutionary synthesis. These fields of study show that large-scale evolutionary phenomena cannot be understood solely on the basis of extrapolation from processes observed at the level of modern populations and species. Patterns and rates of evolution are much more varied than had been conceived by Darwin or the evolutionary synthesis, and physical factors of the earth's history have had a significant, but extremely varied, impact on the evolution of life.     

Evolution and Conservation of Central African Biodiversity: Priorities for Future Research and Education in the Congo Basin and Gulf of Guinea

The tropical forests of the Congo Basin and Gulf of Guinea harbor some of the greatest terrestrial and aquatic biological diversity in the world. However, our knowledge of the rich biological diversity of this region and the evolutionary processes that have shaped it remains limited, as is our understanding of the capacity for species to adapt or otherwise respond to current and projected environmental change. In this regard, research efforts are needed to increase current scientific knowledge of this region's biodiversity, identify the drivers of past diversification, evaluate the potential for species to adapt to environmental change and identify key populations for future conservation. Moreover, when evolutionary research is combined with ongoing environmental monitoring efforts, it can also provide an important set of tools for assessing and mitigating the impacts of development activities. Building on a set of recommendations developed at an international workshop held in Gabon in 2011, we highlight major areas for future evolutionary research that could be directly tied to conservation priorities for the region. These research priorities are centered around five disciplinary themes: (1) documenting and discovering biodiversity; (2) identifying drivers of evolutionary diversification; (3) monitoring environmental change; (4) understanding community and ecosystem level processes; (5) investigating the ecology and epidemiology of disease from an evolutionary perspective (evolutionary epidemiology). Furthermore, we also provide an overview of the needs and priorities for biodiversity education and training in Central Africa.     

The population biology of transposable elements

A transposable element can be defined as a DNA sequence capable of moving to new sites in the genome. Such DNA sequences have been described in a wide range of organisms. The evolutionary processes affecting transposable elements can thus be divided into two categories: changes in sequence and changes in genomic location. As with other types of evolutionary change, the nature of the evolutionary process will be reflected in the extent and type of genetic variation existing in wild populations. Quantitative models of the evolution of transposable element sequences and positions will be outlined, and related to relevant data. The extent to which models designed to describe obvious transposable elements such as the mobile sequences of Drosophila are also applicable to interspersed repetitive DNAs from other species will be discussed.     

Evolutionary responses of plants to anthropogenic pollutants

There is currently great concern over the possible adverse effects of atmospheric de position and other regionally distributed pollutants on plants and plant communitics. In Europe and North America there are major research efforts to determine whether such pollutants damage plants or affect ecosystem processes. A topic of growing concern is the possibility of genetic or evolutionary effects of pollutants. Past research has demonstrated that individuals, populations and varieties of a particular species can differ in their response to pollutants. Although such differences have been documented, the importance of evolutionary responses to regional, low level but chronic pollution remains to be established. The significance of regional chronic pollution is that effects on plants may no longer be limited to heavily industrialized or populated areas, but rather may also occur in virtually all natural ecosystems.     

Eco‐evolution on the edge during climate change

We urgently need to predict species responses to climate change to minimize future biodiversity loss and ensure we do not waste limited resources on ineffective conservation strategies. Currently, most predictions of species responses to climate change ignore the potential for evolution. However, evolution can alter species ecological responses, and different aspects of evolution and ecology can interact to produce complex eco‐evolutionary dynamics under climate change. Here we review how evolution could alter ecological responses to climate change on species warm and cool range margins, where evolution could be especially important. We discuss different aspects of evolution in isolation, and then synthesize results to consider how multiple evolutionary processes might interact and affect conservation strategies. On species cool range margins, the evolution of dispersal could increase range expansion rates and allow species to adapt to novel conditions in their new range. However, low genetic variation and genetic drift in small range‐front populations could also slow or halt range expansions. Together, these eco‐evolutionary effects could cause a three‐step, stop‐and‐go expansion pattern for many species. On warm range margins, isolation among populations could maintain high genetic variation that facilitates evolution to novel climates and allows species to persist longer than expected without evolution. This ‘evolutionary extinction debt’ could then prevent other species from shifting their ranges. However, as climate change increases isolation among populations, increasing dispersal mortality could select for decreased dispersal and cause rapid range contractions. Some of these eco‐evolutionary dynamics could explain why many species are not responding to climate change as predicted. We conclude by suggesting that resurveying historical studies that measured trait frequencies, the strength of selection, or heritabilities could be an efficient way to increase our eco‐evolutionary knowledge in climate change biology.     

Co-declining mammals and dung beetles: an impending ecological cascade

Biodiversity loss can precipitate extinction cascades and impair ecological processes. These 'downstream' effects will be exacerbated if functionally important taxa are tightly linked with species threatened by extinction or population decline. We review the current evidence that such a scenario is currently playing out in the linked declines of persistently hunted mammal populations and the dung beetles communities (Coleoptera: Scarabaeidae: Scarabaeinae) that depend on them for adult and larval food resources. Through a close evolutionary association, mammal assemblages have played a fundamental role in structuring extant dung beetle communities. Today many game mammal species' populations are severely depleted by subsistence or commercial hunting, especially in tropical forest systems. Multiple lines of evidence from temperate and tropical systems indicate that the regional-scale decline or extirpation of medium and large bodied mammal faunas can severely disrupt the diversity and abundance of dung beetle communities through alterations in the composition and availability of dung resources. These observed community disassemblies have significant short- and long-term implications for the maintenance of key ecosystem processes including nutrient recycling and secondary seed dispersal. Identifying the species- and community-level traits that buffer or exacerbate these species and functional responses is essential if we are to develop a better understanding of the cascading ecological consequences of hunting in tropical forests.     

A macroecological approach to evolutionary rescue and adaptation to climate change

Despite the widespread use of ecological niche models (ENMs) for predicting the responses of species to climate change, these models do not explicitly incorporate any population‐level mechanism. On the other hand, mechanistic models adding population processes (e.g. biotic interactions, dispersal and adaptive potential to abiotic conditions) are much more complex and difficult to parameterize, especially if the goal is to predict range shifts for many species simultaneously. In particular, the adaptive potential (based on genetic adaptations, phenotypic plasticity and behavioral adjustments for physiological responses) of local populations has been a less studied mechanism affecting species’ responses to climatic change so far. Here, we discuss and apply an alternative macroecological framework to evaluate the potential role of evolutionary rescue under climate change based on ENMs. We begin by reviewing eco‐evolutionary models that evaluate the maximum sustainable evolutionary rate under a scenario of environmental change, showing how they can be used to understand the impact of temperature change on a Neotropical anuran species, the Schneider's toad Rhinella diptycha. Then we show how to evaluate spatial patterns of species’ geographic range shift using such models, by estimating evolutionary rates at the trailing edge of species distribution estimated by ENMs and by recalculating the relative amount of total range loss under climate change. We show how different models can reduce the expected range loss predicted for the studied species by potential ecophysiological adaptations in some regions of the trailing edge predicted by ENMs. For general applications, we believe that parameters for large numbers of species and populations can be obtained from macroecological generalizations (e.g. allometric equations and ecogeographical rules), so our framework coupling ENMs with eco‐evolutionary models can be applied to achieve a more accurate picture of potential impacts from climate change and other threats to biodiversity.     

海洋岛屿生物多样性保育研究进展

海洋岛屿生态系统因具有明显的海域地理隔离而区别于陆地生态系统,被誉为生物地理与进化生态学研究的"天然实验室".陆地或其它邻近岛屿的种源物种迁移到新的岛屿后,经历地理隔离、特征置换或适应辐射等一系列的岛屿进化过程,形成与种源物种具有显著遗传差异的岛屿特有种.岛屿在小面积范围内分化形成大量的特有种,是岛屿生物多样性最为重要的特点之一.但是,岛屿种群由于分布范围局限、生境脆弱且种群规模较小,岛屿种群较陆地种群具有更高的灭绝风险.本文通过对海洋岛屿物种的起源与演化、遗传结构以及岛屿物种的濒危与保护3个热点问题的讨论,阐述岛屿生物多样性的形成机制、濒危肇因以及岛屿生物多样性保育的重要性.     

Montane refuges and topographic complexity generate and maintain invertebrate biodiversity: recurring themes across space and time

If a common set of landscape characteristics seem to predict spatial patterns of biodiversity in several regions with different biogeographic histories and community compositions, these could inform conservation. Two papers recently published in Journal of Insect Conservation provided evidence that topographic heterogeneity can play a major role in harbouring invertebrate community biodiversity, and that upland areas potentially function as refugia from infrequent but severe climatic conditions that occur over ecological timescales. Similar findings are being echoed in the growing body of phylogeographic literature on terrestrial invertebrates from montane landscape settings. The purpose of this short communication is to place the two recently published papers into a broader context. Phylogeographic studies usually focus on genetic diversity within and among populations, and at relatively deep evolutionary timescales. The parallels that appear to be emerging across different levels of biological organisation and temporal spectra suggest that (1) microevolutionary processes operating at the level of populations may ‘scale-up’ to macroevolutionary processes operating at the level of species or higher, and (2) certain landscape features—particularly topography—may be particularly important when formulating strategies to protect terrestrial invertebrate biodiversity.