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The demography of range boundaries versus range cores in eastern US tree species.

ABSTRACT: Regional species-climate correlations are well documented, but little is known about the ecological processes responsible for generating these patterns. Using the data from over 690,000 individual trees I estimated five demographic rates--canopy growth, understorey growth, canopy lifespan, understorey lifespan and per capita reproduction--for 19 common eastern US tree species, within the core and the northern and southern boundaries, of the species range. Most species showed statistically significant boundary versus core differences in most rates at both boundary types. Differences in canopy and understorey growth were relatively small in magnitude but consistent among species, being lower at the northern (average -17%) and higher at the southern (average +12%) boundaries. Differences in lifespan were larger in magnitude but highly variable among species, except for a marked trend for reduced canopy lifespan at the northern boundary (average -49%). Differences in per capita reproduction were large and statistically significant for some species, but highly variable among species. The rate estimates were combined to calculate two performance indices: R(0) (a measure of lifetime fitness in the absence of competition) was consistently lower at the northern boundary (average -86%) whereas Z* (a measure of competitive ability in closed forest) showed no sign of a consistent boundary-core difference at either boundary.

SUBMITTER: Purves DW

PROVIDER: S-EPMC2677233 | biostudies-literature | 2009 Apr

REPOSITORIES: biostudies-literature

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The demography of range boundaries versus range cores in eastern US tree species.

Purves Drew W DW

Proceedings. Biological sciences 20090225 1661

Regional species-climate correlations are well documented, but little is known about the ecological processes responsible for generating these patterns. Using the data from over 690,000 individual trees I estimated five demographic rates--canopy growth, understorey growth, canopy lifespan, understorey lifespan and per capita reproduction--for 19 common eastern US tree species, within the core and the northern and southern boundaries, of the species range. Most species showed statistically signif ...[more]

PMID: 19324819

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Project description:BackgroundMarine species constitute commercially important resources, and knowledge about mechanisms that shape phylogeographic patterns and genetic structure provides valuable information for conservation. The dolphinfish, Coryphaena hippurus, is one of the most important species caught in the Tropical Eastern Pacific (TEP). However, the lack of consensus about the existence of genetically differentiated populations in the area has hindered the adoption of management strategies to ensure its viability.MethodsWe assessed genetic variation and phylogeographic structure using two mitochondrial genes and 14 nuclear DNA microsatellite loci. Population genetic tools were used to characterize the spatial distribution of genetic variation of C. hippurus in the TEP, evaluate the extent of connectivity between dolphinfish populations, infer potential barriers to gene flow, and test for signals of contemporary and historical demographic expansions.ResultsMitochondrial DNA sequences showed genetic homogeneity across locations in the TEP, as well as a strong signal of population expansion dated to the late Pleistocene. In contrast, nuclear microsatellite markers resolved four genetically distinct groups with a remarked genetic differentiation between the most distant locations, at the northern and southern boundaries of the species' range. High mean genetic diversity was found at all localities (Hs = 0.66-0.81). Notwithstanding, positive F IS and low effective population size (Ne = 77.9-496.4) were also recorded.ConclusionsThe distribution of genetic variation could be related to expansion-contraction cycles following seasonal temperature changes at transitional areas, promoting population subdivisions. However, we cannot rule out the effect of oceanographic dynamics to the observed patterns. Although this marine species remains highly abundant despite commercial exploitation, the low Ne values are of conservation concern and must be considered in fishery management plans.

Dataset Information

The demography of range boundaries versus range cores in eastern US tree species.

Publications

The demography of range boundaries versus range cores in eastern US tree species.

Similar Datasets

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