How do geometric constraints influence migration patterns? (original) (raw)
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A COMPARATIVE STUDY OF ASYMMETRIC MIGRATION EVENTS ACROSS A MARINE BIOGEOGRAPHIC BOUNDARY
Evolution, 2001
In many nonclonal, benthic marine species, geographic distribution is mediated by the dispersal of their larvae. The dispersal and recruitment of marine larvae may be limited by temperature gradients that can affect mortality or by ocean currents that can directly affect the movements of pelagic larvae. We focus on Point Conception, a wellknown biogeographic boundary between the Californian and Oregonian biogeographic provinces, to investigate whether ocean currents affect patterns of gene flow in intertidal marine invertebrates. The predominance of pelagically dispersing species with northern range limits at Point Conception suggests that ocean currents can affect species distributions by erecting barriers to the dispersal of planktonic larvae. In this paper, we investigate whether the predominantly southward currents have left a recognizable genetic signature in species with pelagically dispersing larvae whose ranges span Point Conception. We use patterns of genetic diversity and a new method for inferring cladistic migration events to test the hypothesis that southward currents increase southward gene flow for species with pelagically dispersing larvae. We collected mitochondrial DNA (mtDNA) sequence data for the barnacles Balanus glandula and Chthamalus fissus and also reanalyzed a previously published mtDNA dataset (Strongylocentrotus purpuratus, Edmands et al. 1996). For all three species, our cladistic approach identified an excess of southward migration events across Point Conception. In data from a fourth species with nondispersing larvae (Nucella emarginata, Marko 1998), our method suggests that ocean currents have not played a role in generating genetic structure.
Incorporating movement in species distribution models
Movement in the context of species distribution models (SDMs) generally refers to a species' ability to access suitable habitat. Movement ability can be determined by some combination of dispersal constraints or migration rates, landscape factors such as patch configuration, disturbance, and barriers, and demographic factors related to age at maturity, mortality, and fecundity. Including movement ability can result in more precise projections that help to distinguish suitable habitat that is or can be potentially occupied, from suitable habitat that is inaccessible. While most SDM studies have ignored movement or conceptualized it in overly simplistic ways (e.g. no dispersal versus unlimited dispersal), it is increasingly important to incorporate realistic information on movement ability, particularly for studies that aim to project future distributions such as climate change forecasting and invasive species applications. This progress report addresses the increasingly complex ways in which movement has been incorporated in SDM and outlines directions for further study.
Implications of movement for species distribution models - Rethinking environmental data tools
The Science of the total environment, 2018
Movement is considered an essential process in shaping the distributions of species. Nevertheless, most species distribution models (SDMs) still focus solely on environment-species relationships to predict the occurrence of species. Furthermore, the currently used indirect estimates of movement allow to assess habitat accessibility, but do not provide an accurate description of movement. Better proxies of movement are needed to assess the dispersal potential of individual species and to gain a more practical insight in the interconnectivity of communities. Telemetry techniques are rapidly evolving and highly capable to provide explicit descriptions of movement, but their usefulness for SDMs will mainly depend on the ability of these models to deal with hitherto unconsidered ecological processes. More specifically, the integration of movement is likely to affect the environmental data requirements as the connection between environmental and biological data is crucial to provide relia...
Biology Letters
The workshop ‘Spatial models in animal ecology, management and conservation’ held at Silwood Park (UK), 9–11 March 2010, aimed to synthesize recent progress in modelling the spatial dynamics of individuals, populations and species ranges and to provide directions for research. It brought together marine and terrestrial researchers working on spatial models at different levels of organization, using empirical as well as theory-driven approaches. Different approaches, temporal and spatial scales, and practical constraints predominate at different levels of organization and in different environments. However, there are theoretical concepts and specific methods that can fruitfully be transferred across levels and systems, including: habitat suitability characterization, movement rules, and ways of estimating uncertainty.
Spatial Models for Species-Area Curves
Journal of Theoretical Biology, 1996
Inspired by earlier work of Hubbell, we introduce a simple spatial model to explain observed species-area curves. As in the theory of MacArthur and Wilson, our curves result from a balance between migration and extinction. Our model predicts that the wide range of slopes of species-area curves is due to the differences in the rates at which new species enter this system. However, two other predictions, that the slope increases with increasing migration/mutation and that the curves for remote islands are flatter than those for near islands, are at odds with some interpretations of data. This suggests either that the data have been misinterpreted, or that the model is not sufficient to explain them.
Non-null Effects of the Null Range in Biogeographic Models: Exploring Parameter
Historical biogeography seeks to understand the distribution of biodiversity in space and time. The dispersal-extinction-cladogenesis (DEC) model, a likelihood-based model of geographic range evolution, is widely used in assessing the biogeography of clades. Robust inference of dispersal and local extinction parameters is crucial for biogeographic inference, and yet a major caveat to its use is that the DEC model severely underestimates local extinction. We suggest that this is mainly due to the way in which the model is constructed to allow observed species to transition into being present in no areas (i.e., null range). By prohibiting transitions into the null range in the transition rate matrix, we were able to better infer local extinction and support this with simulations. This modified model, DEC*, has higher model fit and model adequacy than DEC, suggesting this modification should be considered for DEC and other models of geographic range evolution.
Biology Letters, 2010
The workshop “Spatial models in ecology, management and conservation” held at Silwood Park (UK), 9-11 March 2010, aimed to synthesize recent progress in modelling the spatial dynamics of individuals, populations and species ranges and to provide directions for research. It brought together marine and terrestrial researchers working on spatial models at different levels of organisation, and using empirical as well as theory-driven approaches. Different approaches, temporal and spatial scales, and practical constraints predominate at different levels of organisation and in different environments. However, there are theoretical concepts and specific methods that can fruitfully be transferred across levels and systems, including: habitat suitability characterisation, movement rules, and ways of estimating uncertainty.
Geometric constraints and spatial pattern of species richness: critique of range-based null models
Diversity and Distributions, 2002
Abstract. Does the shape of a biogeographical region influence its spatial patterns of species richness? A complete answer must include careful distinction between the distribution of a species, which is a complex geometric object, and the range of a species, which is relatively simple, especially when reduced to one dimension. We consider range-based models of species richness, in particular range overlap counts in one dimension, for which we give a unified mathematical treatment via the joint probability P(m,l) of midpoints and lengths of ranges. We discuss a number of difficulties, in practice and in principle, using range-based models, and show that the so-called mid-domain effect, a proposed null model for the effect of geometric constraint, is qualitatively a property of all biologically realistic models based on range overlap counts. As such, range-based models provide little insight into understanding or explaining biogeographical patterns in species richness. We characterize the quantitative null model for range overlap counts in one dimension, for which we give a simple and direct field test based on P(m,l). We apply this test to a large clade in a complete bioregion (the Proteaceae of the Cape Floristic Region): geometric constraint does not explain the spatial pattern in this case. We show that any geometric constraint on species richness, including range overlap counts, must act via edge effects. Thus, to understand biogeographical patterns, an understanding of the effects and consequences of edges is fundamental.
Long-distance dispersal: a framework for hypothesis testing
Trends in Ecology & Evolution, 2012
Tests of hypotheses about the biogeographical consequences of long-distance dispersal have long eluded biologists, largely because of the rarity and presumed unpredictability of such events. Here, we examine data for terrestrial (including littoral) organisms in the Pacific to show that knowledge of dispersal by wind, birds and oceanic drift or rafting, coupled with information about the natural environment and biology of the organisms, can be used to generate broad biogeographic predictions. We then examine the predictions in the context of the origin, frequency of arrival and location of establishment of dispersed organisms, as well as subsequent patterns of endemism and diversification on remote islands. The predicted patterns are being increasingly supported by phylogenetic data for both terrestrial and littoral organisms.