Taxon Cycle Research Articles

Flying snails: immigrant selection and the taxon cycle in Pacific Island land snails

Flying snails: immigrant selection and the taxon cycle in Pacific Island land snails

Slowing taxon cycle can explain biodiversity patterns on islands: Insights into the biogeography of the tropical South Pacific from molecular data

AbstractIslands in the tropical Pacific Ocean are renowned for high biodiversity and endemism despite having relatively small landmasses. However, our knowledge of how this biodiversity is formed remains limited. The taxon cycle, where well‐dispersed, earlier colonizers become displaced from coastal to inland habitats by new waves of colonizers, producing isolated, range‐restricted species, has been proposed to explain current biodiversity patterns. Here, we integrate the outcomes of phylogenetic studies in the region to investigate the sources, age, number of colonizations, and diversification of 16 archipelagos in the tropical and subtropical South Pacific. We then evaluate whether the results support the taxon cycle as a plausible mechanism for these observations. We find that most species in the Pacific arrived less than 5 Mya from geographically close sources, suggesting that colonization by new taxa is a frequent and ongoing process. Therefore, our findings are broadly consistent with the theory of the Taxon Cycle, which posits that ongoing colonization results in the gradual displacement of established lineages. Only the oldest archipelagos, New Caledonia and Fiji, do not conform to this trend, having proportionally less recent colonization events, suggesting that the taxon cycle may slow on older islands. This conclusion is further validated by New Caledonia having lower diversification rate estimates than younger islands. We found that diversification rates across archipelagos are negatively correlated with area and age. Therefore, a taxon cycle that slows with island age appears to be a suitable concept for understanding the dynamic nature and biodiversity patterns of the Pacific Islands.

Flea (Insecta: Siphonaptera) Family Diversity

This overview of extant Siphonaptera lists 19 families with major hosts and their general distribution, estimated numbers of genera, species, and subspecies, with a brief taxonomic and phylogenetic review. With around 10 new species described annually, extant flea fauna comprises an estimated 249 genera, 2215 species, and 714 subspecies globally, mostly mammal parasites, but 5% of species are on birds. Host specificity varies from euryxenous (i.e., infesting two or more host orders) (e.g., cat fleas, Ctenocephalides felis felis) to monoxenous (e.g., rabbit fleas, Spilopsyllus cuniculi). The largest family is the paraphyletic Hystrichopsyllidae, making up a third of all flea species. The largest monophyletic family, Ceratophyllidae (rodent and bird fleas), comprises another 20% and has dispersed to every continent, including Antarctica. Fleas descend from scorpionflies (Mecoptera), possibly snow scorpionflies (Boreidae) or Nannochoristidae, and even giant fossils found from the Mesozoic could be Siphonaptera. The diversification of fleas shows evidence of taxon cycles. “Relict” families, such as helmet fleas (Stephanocircidae), have a disjunct distribution reflecting the breakup of Gondwanaland 70 million years ago. “Niche specialists” include nest fleas (Anomiopsyllus), bat fleas (Ischnopsyllidae), and burrowing fleas, such as chigoes (Tungidae). By contrast, Ceratophyllidae fleas could be considered “great speciators”. Cat fleas and several other synanthropic flea species are invasive “supertramps”. Although those species are intensively studied, many flea species and their hosts require urgent surveys and conservation.

Taxon Cycles in Neotropical Mangroves.

The concept of the taxon cycle involves successive range expansions and contractions over time, through which a species can indefinitely maintain its core distribution. Otherwise, it becomes extinct. Taxon cycles have been defined mostly for tropical island faunas; examples from continental areas are scarce, and similar case studies for plants remain unknown. Most taxon cycles have been identified on the basis of phylogeographic studies, and straightforward empirical evidence from fossils is lacking. Here, empirical fossil evidence is provided for the recurrent Eocene to the present expansion/contraction cycles in a mangrove taxon (Pelliciera) after a Neotropical-wide study of the available pollen records. This recurrent behavior is compatible with the concept of the taxon cycle from biogeographical, chronological and ecological perspectives. The biotic and abiotic drivers potentially involved in the initiation and maintenance of the Pelliciera expansion/contraction cycles are analyzed, and the ecological and evolutionary implications are discussed. Whether this could be a trend toward extinction is considered under the predictions of the taxon cycle theory. The recurrent expansion and contraction cycles identified for Pelliciera have strong potential for being the first empirically and unequivocally documented taxon cycles and likely the only taxon cycles documented to date for plants.

In Memoriam : Edward O. Wilson (1929-2021): It All Started with Ants.

In Memoriam : Edward O. Wilson (1929-2021): It All Started with Ants.

Tramps in transition: genetic differentiation between populations of an iconic "supertramp" taxon in the Central Indo-Pacific

The island monarch (Monarcha cinerascens) was an original example of the “supertramp strategy”. This involves well-developed dispersal specialisation, enabling a species to colonise remote islands but leaving it competitively inferior. Supertramps are hypothesised to be excluded from larger islands by superior competitors. It is the only original Melanesian supertramp to occur in Wallacea, home also to the sedentary pale-blue monarch (Hypothymis puella). We interrogate the supertramp strategy and its biogeographical underpinnings by assessing the population structure of these two monarchs. We sampled island and pale-blue monarchs in Wallacea, collecting DNA and morphological data. We investigated monarch population structure by applying ABGD and Bayesian and Maximum Likelihood methods to their ND2 and ND3 genes. We constructed linear models to investigate the relationships between genetic divergence, dispersal ability, and island area, elevation, and isolation. Wallacea’s deep waters restrict gene flow even in a supertramp, as the Wallacean and Melanesian island monarchs are likely separate species (mean genetic distance: 2.7%). This mirrors the split of the pale-blue monarch from Asia’s black-naped monarch (Hypothymis azurea). We found further population structure within Wallacean and Melanesian island monarch populations. Their genetic divergence was related to elevation, area, and isolation of islands, as well as dispersal ability of birds. However, dispersal ability was independent of island elevation and area. Rather than being r-selected on small, disturbance-prone islands, our results support the view that the island monarch’s supertramp lifestyle is a temporary stage of the taxon cycle, i.e. supertramps may transition into resident species after colonisation. Our models suggest that more dispersive monarchs reach more distant islands, and divergence is promoted on islands that are more distant or larger or more permanent, without selection against dispersal ability per se. We suggest that supertramp lifestyle helps determine the distribution of species across islands, not necessarily the divergence occurring thereafter.

On the macroecological significance of eco-evolutionary dynamics: the range shift-niche breadth hypothesis.

Global correlations of range size and niche breadth, and their relationship to latitude, have long intrigued ecologists and biogeographers. Study of these patterns has given rise to a number of hypothesized ecological and evolutionary processes purported to shape biogeographic outcomes, including the climate variability hypothesis, oscillation hypothesis, ecological opportunity, competitive release and taxon cycles. Here, I introduce the alternative range shift-niche breadth hypothesis, which posits that broader niches and larger range sizes are jointly determined under eco-evolutionary processes unique to expanding ranges, which may or may not be adaptive, but which co-shape observed latitudinal gradients in niche breadth and range size during periods of widespread range expansion. I formulate this hypothesis in comparison against previous hypotheses, exploring how each relies on equilibrium versus non-equilibrium evolutionary processes, faces differing issues of definition and scale, and results in alternative predictions for comparative risk and resilience of global ecosystems. Such differences highlight that accurate understanding of process is critical when applying macroecological insight to biodiversity forecasting. Furthermore, past conceptual emphasis on a central role of local adaptation under equilibrium conditions may have obscured a ubiquitous role of non-equilibrium evolutionary processes for generating many important, regional and global macroecological patterns. This article is part of the theme issue 'Species' ranges in the face of changing environments (part I)'.

Patterns of host tree use within a lineage of saproxlic snout-less weevils (Coleoptera: Curculionidae: Scolytinae: Scolytini)

The influence of plants in the diversification of herbivorous insects, specifically those that utilize moribund and dead hosts, is little explored. Host shifts are expected because the effectiveness of toxic secondary chemicals is lessened by decay of dead plants. Feeding on dead plants also releases herbivorous insect lineages from diversifying within a particular plant lineage. Thus, phylogenetic constraints on the herbivorous insect lineage imposed by the host plants are diminished and repeated patterns of species diversification in an association with unrelated host trees is hypothesized (i.e., taxon cycle). Scolytini, a diverse weevil tribe, specialize on many different dead and moribund plant taxa as a source of food. These species and their hosts offer an opportunity to examine the association between dead host plants and the extent of phylogenetic constraints. A phylogeny of the Scolytini was reconstructed with likelihood and Bayesian analyses of DNA sequence data from nuclear (28S, CAD, ArgK) and mitochondrial (COI) genes. Ancestral host usage and geography was reconstructed using likelihood criteria and conservation of host use was tested. Results supported a monophyletic Scolytini, Ceratolepis, Loganius, and a paraphyletic Scolytus, Camptocerus and Cnemonyx. Diversification of the Scolytini generally occurred well after their host taxa diversified and suggests a sequential evolution of host use. In this scenario the beetle imposes little selection pressure on the tree but the tree provides a platform for beetle evolution. Major changes in host tree use occurred during periods of global cooling associated with changes in beetle biogeography. Diversification of beetles occurred on common and widespread hosts and there was likely a single origination of conifer-feeding from angiosperm-feeding species during the early Pliocene and a radiation of beetle species from the Palearctic to the Nearctic. Overall, the observed patterns of Scolytini host use are conserved and are similar to those expected in a taxon pulse diversification. That is, after a host switch to an unrelated tree, the beetles diversify within the host plant lineage. The need to locate an ephemeral food resource, i.e., a dying tree, likely maintains host specificity once a host shift occurs. These findings suggest that characteristics of dead and moribund host plants (e.g. secondary chemicals) influence the diversification of these saproxlic weevils despite the reduction of selection pressures.

Influence of niche breadth and position on the historical biogeography of seafaring scincid lizards

AbstractNiche breadth and position can influence diversification among closely related species or populations, yet limited empirical data exist concerning the predictability of the outcomes. We explored the effects of these factors on the evolution of the Emoia atrocostata species group, an insular radiation of lizards in the western Pacific Ocean and Indo-Australasia composed of both endemic and widespread species that differ in niche occupancy. We used molecular data and phylogeographical diffusion models to estimate the timing and patterns of range expansion, and ancestral reconstruction methods to infer shifts in ecology. We show evidence of multidirectional spread from a centre of origin in western Micronesia, and that the phyletic diversity of the group is derived from a putative habitat specialist that survives in the littoral zone. This species is composed of paraphyletic lineages that represent stages or possible endpoints in the continuum toward speciation. Several descendant species have transitioned to either strand or interior forest habitat, but only on remote islands with depauperate terrestrial faunas. Our results suggest that the atrocostata group might be in the early phases of a Wilsonian taxon cycle and that the capacity to tolerate salt stress has promoted dispersal and colonization of remote oceanic islands. Divergence itself, however, is largely driven by geographical isolation rather than shifts in ecology.

Colonize, radiate, decline: Unraveling the dynamics of island community assembly with Fijian trap-jaw ants.

The study of island community assembly has been fertile ground for developing and testing theoretical ideas in ecology and evolution. The ecoevolutionary trajectory of lineages after colonization has been a particular interest, as this is a key component of understanding community assembly. In this system, existing ideas, such as the taxon cycle, posit that lineages pass through a regular sequence of ecoevolutionary changes after colonization, with lineages shifting toward reduced dispersal ability, increased ecological specialization, and declines in abundance. However, these predictions have historically been difficult to test. Here, we integrate phylogenomics, population genomics, and X‐ray microtomography/3D morphometrics, to test hypotheses for whether the ecomorphological diversity of trap‐jaw ants (Strumigenys) in the Fijian archipelago is assembled primarily through colonization or postcolonization radiation, and whether species show ecological shifts toward niche specialization, toward upland habitats, and decline in abundance after colonization. We infer that most Fijian endemic Strumigenys evolved in situ from a single colonization and have diversified to fill a large fraction of global morphospace occupied by the genus. Within this adaptive radiation, lineages trend to different degrees toward high elevation, reduced dispersal ability, and demographic decline, and we find no evidence of repeated colonization that displaces the initial radiation. Overall these results are only partially consistent with taxon cycle and associated ideas, while highlighting the potential role of priority effects in assembling island communities.

Genomic and phenomic analysis of island ant community assembly.

Island biodiversity has long fascinated biologists as it typically presents tractable systems for unpicking the eco-evolutionary processes driving community assembly. In general, two recurring themes are of central theoretical interest. First, immigration, diversification, and extinction typically depend on island geographical properties (e.g., area, isolation, and age). Second, predictable ecological and evolutionary trajectories readily occur after colonization, such as the evolution of adaptive trait syndromes, trends toward specialization, adaptive radiation, and eventual ecological decline. Hypotheses such as the taxon cycle draw on several of these themes to posit particular constraints on colonization and subsequent eco-evolutionary dynamics. However, it has been challenging to examine these integrated dynamics with traditional methods. Here, we combine phylogenomics, population genomics and phenomics, to unravel community assembly dynamics among Pheidole (Hymenoptera, Formicidae) ants in the isolated Fijian archipelago. We uphold basic island biogeographic predictions that isolated islands accumulate diversity primarily through in situ evolution rather than dispersal, and population genomic support for taxon cycle predictions that endemic species have decreased dispersal ability and demography relative to regionally widespread taxa. However, rather than trending toward island syndromes, ecomorphological diversification in Fiji was intense, filling much of the genus-level global morphospace. Furthermore, while most endemic species exhibit demographic decline and reduced dispersal, we show that the archipelago is not an evolutionary dead-end. Rather, several endemic species show signatures of population and range expansion, including a successful colonization to the Cook islands. These results shed light on the processes shaping island biotas and refine our understanding of island biogeographic theory.

Biogeography and Ecological Diversification of a Mayfly Clade in New Guinea

Understanding processes that have driven the extraordinary high level of biodiversity in the tropics is a long-standing question in biology. Here we try to assess whether the large lineage richness found in a New Guinean clade of mayflies (Ephemeroptera), namely the Thraulus group (Leptophlebiidae) could be associated with the recent orogenic processes, by applying a combination of phylogenetic, biogeographic and ecological shift analyses. New Guinean representatives of the Thraulus group appear monophyletic, with the possible exception of a weakly-supported early-diverging clade from the Sunda Islands. Dating analyses suggest an Eocene origin of the Thraulus group, predating by several million years current knowledge on the origin of other New Guinean aquatic organisms. Biogeographic inferences indicate that 27 of the 28 inferred dispersals (96.4%) occurred during the Eocene, Oligocene and Miocene, while only one dispersal (3.6%) took place during the Pliocene-Pleistocene. This result contrasts with the higher number of altitudinal shifts (15 of 22; 68.2%) inferred during the Pliocene-Pleistocene time slice. Our study illustrates the role played by – potentially ecological - diversification along the elevation gradient in a time period concomitant with the establishment of high-altitude ecological niches, i.e., during orogenesis of the central New Guinean mountain range. This process might have taken over the previous main mode of diversification at work, characterized by dispersal and vicariance, by driving lineage divergence of New Guinean Leptophlebiidae across a wide array of habitats along the elevation gradient. Additional studies on organisms spanning the same elevation range as Thraulus mayflies in the tropics are needed to evaluate the potential role of the ecological opportunity or taxon cycles hypotheses in partly explaining the latitudinal diversity gradient.

Reconciling supertramps, great speciators and relict species with the taxon cycle stages of a large island radiation (Aves: Campephagidae)

AbstractAimThe taxon cycle concept provides a geographically explicit and testable set of hypotheses for exploring the evolutionary processes underlying the distribution of species in space and time. Here, we test taxon cycle predictions within a large avian island radiation, the core Campephagidae and explicitly integrate the concepts of ‘supertramps’, ‘great speciators’ and relictualization.LocationThe Indo‐Pacific, Australia, Asia and Africa.TaxonCorvoid passerine birds.MethodsWe constructed a new time‐calibrated molecular phylogeny of the core Campephagidae (cuckooshrikes, cicadabirds and trillers) using Bayesian phylogenetic methods. Ancestral range estimation methods and diversification rate analyses were used to explore the dispersal and diversification history of the group. We used an extensive dataset on wing morphology and range distributions to test for correlations between evolutionary age of species and dispersal capacity, diversification and distribution, while accounting for phylogenetic non‐independence.ResultsThe core Campephagidae represents an ecologically homogeneous radiation distributed across the Indo‐Pacific, Australia, Southeast Asia and Africa. Its members represent a continuum of dispersal abilities; some species are widespread and undifferentiated (‘supertramps’) or show strong differentiation of local populations (‘great speciators’), and a few are endemic to single islands (relicts). We show that older species relative to younger species inhabit fewer and larger islands at higher elevations. The level of intraspecific variation measured as the number of subspecies also decreases with species age, and is highest in ‘great speciators’ with intermediate levels of dispersal abilities (as per hand‐wing index).Main conclusionsBased on trait correlations with species age, we infer phases of range expansion and contraction over millions of years (taxon cycles), within a single monophyletic group of birds. These observations demonstrate reconciliation of the concepts of ‘supertramps’, ‘great speciators’ and relictual palaeoendemics within the temporal stages of the taxon cycle.

Phylogenomics clarifies biogeographic and evolutionary history, and conservation status of West Indian tremblers and thrashers (Aves: Mimidae)

The West Indian avifauna has provided fundamental insights into island biogeography, taxon cycles, and the evolution of avian behavior. Our interpretations, however, should rely on robust hypotheses of evolutionary relationships and consistent conclusions about taxonomic status in groups with many endemic island populations. Here we present a phylogenetic study of the West Indian thrashers, tremblers, and allies, an assemblage of at least 5 species found on 29 islands, including what is considered the Lesser Antilles’ only avian radiation. We improve on previous phylogenetic studies of this group by using double-digest restriction site-associated DNA sequencing (ddRAD-seq) to broadly sample loci scattered across the nuclear genome. A variety of analyses, based on either nucleotide variation in 2223 loci recovered in all samples or at 13,282 loci confidently scored as present or absent in all samples, converged on a single well-supported phylogenetic hypothesis. Results indicate that the resident West Indian taxa form a monophyletic group, exclusive of the Neotropical–Nearctic migratory Gray Catbird Dumetella carolinensis, which breeds in North America; this outcome differs from earlier studies suggesting that Gray Catbird was nested within a clade of island resident species. Thus, our findings imply a single colonization of the West Indies without the need to invoke a subsequent ‘reverse colonization’ of the mainland by West Indian taxa. Additionally, our study is the first to sample both endemic subspecies of the endangered White-breasted Thrasher Ramphocinclus brachyurus. We find that these subspecies have a long history of evolutionary independence with no evidence of gene flow, and are as genetically divergent from each other as other genera in the group. These findings support recognition of R. brachyurus (restricted to Martinique) and the Saint Lucia Thrasher R. sanctaeluciae as two distinct, single-island endemic species, and indicate the need to re-evaluate conservation plans for these taxa. Our results demonstrate the utility of phylogenomic datasets for generating robust systematic hypotheses.

Why is fruit colour so variable? Phylogenetic analyses reveal relationships between fruit‐colour evolution, biogeography and diversification

AbstractAimAre different fruit colours related to large‐scale patterns of dispersal, distribution and diversification? Here, we investigate this question for the first time, using phylogenetic approaches in the tribe Gaultherieae (Ericaceae). We test relationships between fruit colour and (a) biogeographic dispersal, (b) elevational and latitudinal species distributions and (c) rates of diversification.LocationGlobal.Time periodRecent to 30 million years ago.Major taxa studiedThe plant tribe Gaultherieae in the family Ericaceae (blueberries and relatives).MethodsWe estimated a new time‐calibrated phylogeny for Gaultherieae. Data on fruit colours and geographic distributions for each species were compiled from published sources and field observations. Using phylogenetic methods, we estimated major dispersal events across the tree and the most likely fruit colour associated with each dispersal event, and tested whether dispersal between major biogeographic regions was equally likely for different fruit colours, and whether dispersal distances were larger for certain colours. We then tested the relationships between fruit colours and geographic variables (latitude, elevation) and diversification rates.ResultsLarge‐scale dispersal events were significantly associated with red‐fruited lineages, even though red‐fruited species were relatively uncommon. Further, different fruit colours were associated with different elevations and latitudes (e.g. red at lower elevations, violet at lower latitudes, white at higher elevations). Violet colour was related to increased diversification rates, leading to more violet‐fruited species globally.Main conclusionsOverall, we show that different fruit colours can significantly impact the large‐scale dispersal, distribution and diversification of plant clades. Furthermore, the interplay between biogeography and fruit‐colour evolution seems to generate “taxon cycles” in fruit colour that may drive variation in fruit colour over macroevolutionary time‐scales.

Taxon cycle predictions supported by model-based inference in Indo-Pacific trap-jaw ants (Hymenoptera: Formicidae: Odontomachus).

Nonequilibrium dynamics and non-neutral processes, such as trait-dependent dispersal, are often missing from quantitative island biogeography models despite their potential explanatory value. One of the most influential nonequilibrium models is the taxon cycle, but it has been difficult to test its validity as a general biogeographical framework. Here, we test predictions of the taxon cycle model using six expected phylogenetic patterns and a time-calibrated phylogeny of Indo-Pacific Odontomachus (Hymenoptera: Formicidae: Ponerinae), one of the ant genera that E.O. Wilson used when first proposing the hypothesis. We used model-based inference and a newly developed trait-dependent dispersal model to jointly estimate ancestral biogeography, ecology (habitat preferences for forest interiors, vs. "marginal" habitats, such as savannahs, shorelines, disturbed areas) and the linkage between ecology and dispersal rates. We found strong evidence that habitat shifts from forest interior to open and disturbed habitats increased macroevolutionary dispersal rate. In addition, lineages occupying open and disturbed habitats can give rise to both island endemics re-occupying only forest interiors and taxa that re-expand geographical ranges. The phylogenetic predictions outlined in this study can be used in future work to evaluate the relative weights of neutral (e.g., geographical distance and area) and non-neutral (e.g., trait-dependent dispersal) processes in historical biogeography and community ecology.

Phylogeography of a ‘great speciator’ (Aves:Edolisoma tenuirostre) reveals complex dispersal and diversification dynamics across the Indo‐Pacific

AbstractAimWe derive a new phylogenetic framework of the Indo‐Pacific avian genusEdolisomabased on a dense taxon sampling and use it in an explicit spatiotemporal framework to understand the history of intraspecific diversification dynamics in a ‘great speciator’, the CicadabirdEdolisoma tenuirostre/remotumcomplex.LocationThe Indo‐Pacific island region, Australia and New Guinea.TaxonCorvoid passerine birds (Passeriformes).MethodsWe used Bayesian phylogenetic methods (beast) to construct a time‐calibrated molecular phylogeny of all 19 species in the genusEdolisomaand 27 of 29 subspecies of theE. tenuirostre/remotumcomplex (previouslyCoracina tenuirostris) primarily based on one mitochondrial DNA marker. Ancestral area reconstruction methods (‘BioGeoBEARS’) were used to infer the historical biogeography of the genus. We used population‐level analyses to assess intraspecific phylogeography and a molecular species delimitation test to evaluate the current taxonomy. A morphometric dataset was used to discuss differential dispersal ability among taxa.ResultsEdolisomaoriginated in the late Miocene and diversification within theE. tenuirostre/remotumcomplex began in the Pleistocene. Within the North Melanesian and North Wallacean archipelagos, which have experienced several waves of diversification, we find significant patterns of genetic isolation by distance, but not within the Australo‐Papuan ‘mainland’, which was recently back‐colonized from these archipelagos. Based on the phylogeny, we suggest several taxonomic changes. We also discuss evidence of taxon cycles withinEdolisomabased on correlations of species age, elevational ranges and dispersal ability.Main conclusionsThe biogeographical history and patterns of differentiation between phylogroups withinE. tenuirostresupport the importance of barriers to gene flow in island systems. Examples of both recent genetic exchange across significant sea barriers and differentiation across much smaller water gaps suggest complex dispersal and diversification dynamics. The capacity for dispersal away from islands, and gradual shifts in dispersal ability in relation to the geographical setting, is supported as important factors in generating a ‘great speciator’.

Lizards of the lost arcs: mid-Cenozoic diversification, persistence and ecological marginalization in the West Pacific.

Regions with complex geological histories often have diverse and highly endemic biotas, yet inferring the ecological and historical processes shaping this relationship remains challenging. Here, in the context of the taxon cycle model of insular community assembly, we investigate patterns of lineage diversity and habitat usage in a newly characterized vertebrate radiation centred upon the world's most geologically complex insular region: island arcs spanning from the Philippines to Fiji. On island arcs taxa are ecologically widespread, and provide evidence to support one key prediction of the taxon cycle, specifically that interior habitats (lowland rainforests, montane habitats) are home to a greater number of older or relictual lineages than are peripheral habitats (coastal and open forests). On continental fringes, however, the clade shows a disjunct distribution away from lowland rainforest, occurring in coastal, open or montane habitats. These results are consistent with a role for biotic interactions in shaping disjunct distributions (a central tenant of the taxon cycle), but we find this pattern most strongly on continental fringes not islands. Our results also suggest that peripheral habitats on islands, and especially island arcs, may be important for persistence and diversification, not just dispersal and colonization. Finally, new phylogenetic evidence for subaerial island archipelagos (with an associated biota) east of present-day Wallace's Line since the Oligocene has important implications for understanding long-term biotic interchange and assembly across Asia and Australia.

Agricultural intensification during the Late Holocene rather than climatic aridification drives the population dynamics and the current conservation status ofMicrotus cabrerae, an endangered Mediterranean rodent

AbstractAimDisentangling the relative importance of climatic and anthropogenic factors is crucial in conservation biology but problematic using short‐term data only. Long‐term (palaeobiological) data are thus increasingly being used to understand taxon history and to identify potential status and baseline (pre‐anthropogenic) conditions, which in turn allows the optimization of species conservation plans. We combined species distribution models (SDMs) with current and palaeo‐occurrences ofMicrotus cabrerae, a threatened Mediterranean rodent, to circumvent the limitations of the palaeorecord (e.g. spatio‐temporal bias), to characterize this rodent's history (potential status and baseline conditions) since the Mid‐Holocene (~6,000 yr BP), and to determine the relative importance of climatic and anthropogenic factors in its decline.LocationHistoric distributional range ofM. cabrerae(Iberian Peninsula andSEFrance).MethodsWe used generalized linear models (GLMs) to study the effects of four climatic (temperature and precipitation seasonality, minimum temperature, aridity) and four anthropogenic variables (human influence index, surface area of irrigated crops, rain‐fed crops and pastures) on the species’ current distribution. Then, we used an ensemble ofSDMs to estimate its current and Mid‐Holocene potential distributions based only on climate variables, and validated model projections against current and palaeo records. Finally, suitability maps were analysed to study the species’ range dynamics during the Late Holocene.ResultsMicrotus cabrerae's current distribution is constrained by both climatic and anthropogenic variables. Temperature and precipitation seasonality—but not aridity or minimum temperature—play an important positive role in constraining its distribution, but agriculture is the main human activity that affects it negatively. Climatic changes during the Late Holocene probably led to an expansion of its distribution without fragmentating its range.Main conclusionsContrary to previous hypotheses, under natural conditions,M. cabreraeshould be in an expansive phase of its taxon cycle. Yet, its potential and current conservation status is negatively affected by agricultural habitat destruction, suggesting that conservation strategies should aim to control agricultural intensification.

Evolutionary computation in zoology and ecology.

Evolutionary computational methods have adopted attributes of natural selection and evolution to solve problems in computer science, engineering, and other fields. The method is growing in use in zoology and ecology. Evolutionary principles may be merged with an agent-based modeling perspective to have individual animals or other agents compete. Four main categories are discussed: genetic algorithms, evolutionary programming, genetic programming, and evolutionary strategies. In evolutionary computation, a population is represented in a way that allows for an objective function to be assessed that is relevant to the problem of interest. The poorest performing members are removed from the population, and remaining members reproduce and may be mutated. The fitness of the members is again assessed, and the cycle continues until a stopping condition is met. Case studies include optimizing: egg shape given different clutch sizes, mate selection, migration of wildebeest, birds, and elk, vulture foraging behavior, algal bloom prediction, and species richness given energy constraints. Other case studies simulate the evolution of species and a means to project shifts in species ranges in response to a changing climate that includes competition and phenotypic plasticity. This introduction concludes by citing other uses of evolutionary computation and a review of the flexibility of the methods. For example, representing species’ niche spaces subject to selective pressure allows studies on cladistics, the taxon cycle, neutral versus niche paradigms, fundamental versus realized niches, community structure and order of colonization, invasiveness, and responses to a changing climate.