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We tested the hypothesis that, for land snails, long-distance dispersal across oceans is primarily via aerial dispersal (i.e. wind- or bird-mediated), which likely favors so-called micromolluscs through immigrant selection for small (aerially buoyant) body size. Immigrant selection is a filtering process favoring phenotypes conferring greater capacities for long-distance dispersal. We also tested predictions of E. O. Wilson’s taxon cycle, which hypothesizes that descendant species of island colonists are subject to a series of ecological and evolutionary dynamics, resulting over time in progressively more ecologically specialized island endemics with more limited dispersal capacity. We tested predictions of immigrant selection on aerial dispersal and the taxon cycle in native Pacific Island land snails of the Samoan Islands, Mariana Islands, and Lord Howe Island and neighboring small islands using geographic range, shell size, microhabitat, and elevation data compiled from primary and secondary literature. Single-archipelago endemic species found on multiple islands within an archipelago had significantly larger shell sizes than widespread species found in multiple archipelagos and single-island endemic species. Single-archipelago endemic and single-island endemic species were associated with vegetation and ground/rock microhabitats, respectively, whereas widespread species were more likely to be microhabitat generalists. Single-island endemic species were more likely to occur at high-elevation habitats, while widespread species were more likely to be confined to low-elevation habitats. Consistent with predictions of the taxon cycle and immigrant selection on aerial dispersal, Pacific Island land snails endemic to single islands or archipelagos (i.e. those assumed to be later in the taxon cycle) are more likely to have larger body size (archipelago endemics) and to occupy higher elevations (i.e. island interiors; island endemics) in more specialized microhabitats (all endemics).

The acquisition of evidence pertaining to island syndrome often relies on opportunistic observations, yet prior researchers have gradually compiled a body of examples that collectively shed light on its occurrence patterns and dynamics. Our comprehensive literature review revealed that island syndrome dominantly occurs in angiosperms on oceanic islands, with a notable abundance of taxa exhibiting high endemism and possessing functional traits associated with facultative and generalized biotic interactions. While acknowledging the influence of unequal research interest and sampling efforts on the observed patterns, deviations from prevailing sampling biases evident in global plant databases and herbarium collections lend credence to genuine differences in the occurrence of island syndrome. The disproportionate incidence of island syndrome, delineated by taxonomic groups, traits, and specific islands, can be ascribed to the distinct biogeography of oceanic islands and the presence of idiosyncratic ecological and evolutionary processes that contribute to its development. Within an evolutionary framework, our overarching hypothesis posits island syndrome as a transformative trajectory away from the diverse strategies adopted by mainland plants to the alternative strategies exhibited on islands due to their isolation and ecological simplicity. This perspective fosters a more holistic perspective, encompassing the myriad and graded responses of plants to evolutionary pressures encountered on islands. Rather than dismissing the biased occurrence patterns in the examples of island syndrome, we contend that their underlying insights hold substantial value in formulating a general, mechanistic model that enhances our understanding of the development of island syndrome and its evolutionary implications.

Oceanic islands are global hotspots of biodiversity – many of them harboring marvels of evolution in isolation. Unfortunately, insular biotas are also highly susceptible to extinction, especially following colonization by humans. Here, we assess the influence of humanity on the diversity and biological distinctiveness of mammals inhabiting 37 oceanic islands. We compiled lists of mammals inhabitingthese islands prior to and then following colonization by hominids (including Homo erectus and H. sapiens). We then quantified the dynamics in diversity (as measured by species richness) and distinctiveness (measured as beta-diversity) among islands. We compared mammalian assemblages on islands prior to humanity, following colonization by early hominids and then following colonization by H. sapiens (in the latter case, separating assemblage dynamics resulting from extinctions of native species from the effects of species introductions). As expected, early hominids hardly influenced mammalian diversity or distinctiveness. In contrast, colonization by H. sapiens was initially followed by numerous extinctions and substantial declines in species richness, which then however rebounded to exceed pre-humanity levels. These post-humanity increases in species richness were paradoxically accompanied by substantial declines in distinctiveness among islands. This paradox of anthropogenic enrichment is readily resolved by observing that species introductions to the islands (the sources of the post-humanity surges in species richness) were comprised of a highly redundant set of small species (primarily rats and house mice), resulting in the homogenization and downsizing of island life.

Mammalian paleoecology: using the past to study the present, by Felisa A. Smith, 2021, Johns Hopkins University Press, 260 pp., ISBN 9781421441405 (hardcover).

The nine currently recognized species of moa (Order – Dinornithiformes; Bonaparte 1853) suffered extinction soon after New Zealand was settled by humans.  They were the result of an evolutionary radiation that produced a unique guild of birds – giant, and totally wingless species that evolved in the absence of non-volant mammals.   Recent advances in dating and paleoclimatology, and compilations of data on distributions of the nine species of moa, along with information on the geographic, topographic, climatic and edaphic characteristics of sites from which moa remains have been recovered, enabled us to test whether their evolutionary radiation truly was ‘adaptive’, producing ecologically distinct species.  Randomization, resampling analyses of moa distributions across North and South Islands revealed highly significant geographic and ecological segregation, with different species tending to occupy different islands, regions within islands, or elevations within regions.  Quadratic Discriminant Analyses demonstrated niche segregation at even finer scales, including that based on vegetation-defined habitats and on local climatic, topographic and edaphic conditions.  Moa distributions also appear to have been dynamic over time, shifting in their upper elevational limits as climatic conditions changed and vegetative zones shifted upward during the Holocene Epoch.  Our ongoing studies are building on the results presented here to explore the temporal dynamics of moa distributions, assess differential responses of moa species to natural and anthropogenic drivers, and determine how these forces may have combined to cause the extinction of moa just a few centuries ago.

In 2015, we called upon our colleagues to address a glaring oversight of a potentially transformative frontier in biogeography – the geography of sound (Lomolino et al. 2015).  Our purpose here is to lay the conceptual foundations, based on the fundamental unifying principles of biogeography, to guide the development of the nascent field of sonoric geography.  We define sonoric geography as an emerging subdiscipline of biogeography that attempts to discover and articulate patterns of geographic variation in the acoustic properties of biological communities and identify the underlying, causal explanations for those patterns.We see at least two major benefits to this initiative.  First, it will advance the field of biogeography by expanding the spectrum of biological properties studied – demonstrating how the field’s fundamental, unifying principles can be applied to a novel component of biological diversity – sound and acoustic assemblages across the principal geographic dimensions (area, isolation, elevation/depth, and latitude).  Second, a research program in sonoric geography will, in synergism, advance the fields of soundscape ecology (Pijanowski et al. 2011, Slabbekoorn 2018) and acoustic ecology (Wrightson 2000) by integrating an explicit geographic context into their conceptual foundations, empirical investigations, and applications for conserving biological diversity, sensu lato—again, all this guided by the fundamental unifying principles of biogeography.

cover: Butterfly logo designed by Mark V. Lomolino for the original Frontiers of Biogeography book , which we are adopting as the logo of this new journal. See the editorial From the Foundations to the Frontiers of Biogeography for further details.

Mammals play important ecological roles in terrestrial ecosystems, with their particular niches and their impacts on energy flow and nutrient cycling being strongly influenced by one of their most fundamental traits--their body size. Body size influences nearly all of the physiological, behavioral, and ecological traits of mammals, and thus, shifts in body size often serve as key mechanisms of adaptation to variation in environmental conditions over space and time. Along with shifts in phenology and distributions, declining body size has been purported to be one of the three universal responses to anthropogenic climate change, yet few studies have been conducted at the spatial and temporal scales appropriate to test this claim. Here, we report that in response to warming of terrestrial ecosystems across North America over the past century, small mammals are decreasing in body size. We further estimate that by 2100 (when global temperatures may have risen some 2.5 to 5.5 °C since 1880), the total anthropogenic decline in body mass of these ecologically and economically important species may range from 10 to 21%. Such shifts in body size of the great multitudes of small mammal populations are, in turn, likely to have major impacts on the structural and functional diversity of terrestrial assemblages across the globe. [ABSTRACT FROM AUTHOR]

Background and Aims The hart's tongue fern (HTF) complex is a monophyletic group composed of five geographically segregated members with divergent abundance patterns across its broad geographic range. We postulated hierarchical systems of environmental controls in which climatic and land-use change drive abundance patterns at the global scale, while various ecological conditions function as finer scale determinants that further increase geographic disparities at regional to local scales. Methods After quantifying the abundance patterns of the HTF complex, we estimated their correlations with global climate and land-use dynamics. Regional determinants were assessed using boosted regression tree models with 18 potential ecological variables. Moreover, we investigated long-term population trends in the USA to understand the interplay of climate change and anthropogenic activities on a temporal scale. Key Results Latitudinal climate shifts drove latitudinal abundance gradients, and regionally different levels of land-use change resulted in global geographic disparities in population abundance. At a regional scale, population isolation, which accounts for rescue effects, played an important role, particularly in Europe and East Asia where several hot spots occurred. Furthermore, the variables most strongly influencing abundance patterns greatly differed by region: precipitation seasonality in Europe; spatial heterogeneity of temperature and precipitation in East Asia; and magnitudes of past climate change, temperature seasonality and edaphic conditions in North America. In the USA, protected populations showed increasing trends compared with unprotected populations at the same latitude, highlighting the critical role of habitat protection in conservation measures. Conclusions Geographic disparities in the abundance patterns of the HTF complex were determined by hierarchical systems of environmental controls, wherein climatic and land-use dynamics act globally but are modulated by various regional and local determinants operating at increasingly finer scales. We highlighted that fern conservation must be tailored to particular geographic contexts and environmental conditions by incorporating a better understanding of the dynamics acting at different spatiotemporal scales. [ABSTRACT FROM AUTHOR]