Abstract
BackgroundSouthern Appalachian forests are dominated by second-growth vegetation following decades of intensive forestry and agricultural use, although some old-growth patches remain. While it’s been shown that second-growth areas may exhibit comparable species richness to old-growth in the area, the extent to which populations of arthropods in second-growth areas have persisted vs. recolonized from other areas remains unexamined. The implications for conservation of both classes of forest are significant. Here we analyze population diversity and relatedness across five old-growth and five second-growth populations of flightless, leaf litter-inhabiting beetles in the genus Eurhoptus (Coleoptera: Curculionidae: Cryptorhynchinae). Our main goal is asking whether second-growth areas show diminished diversity and/or signals of recolonization from old-growth sources.ResultsPopulation genetic and phylogenetic analyses do not reveal any consistent differences in diversity between the old-growth and second-growth populations examined. Some second-growth populations retain substantial genetic diversity, while some old-growth populations appear relatively depauperate. There is no phylogenetic indication that second-growth populations have recolonized from old-growth source populations.ConclusionsMost populations contain substantial and unique genetic diversity indicating long-term persistence in the majority of sites. The results support substantial resilience in second-growth populations, though the geographic scale of sampling may have hindered detection of recolonization patterns. Broad scale phylogeographic patterns reveal a deep break across the French Broad River basin, as has been reported in several other taxa of limited dispersal abilities. In Eurhoptus this break dates to ~ 2–6 Ma ago, on the older end of the range of previously estimated dates.
Highlights
Southern Appalachian forests are dominated by second-growth vegetation following decades of intensive forestry and agricultural use, some old-growth patches remain
While the majority of Appalachian forests have been heavily impacted by anthropogenic pressures, patches of Caterino and Langton-Myers BMC Evolutionary Biology (2018) 18:165 old-growth forests that have escaped at least some of these effects remain [8]
We recently examined similarity in species composition across the litter beetle communities from a network of old-growth and second-growth sites, scattered across western North Carolina and upstate South Carolina [21]; second-growth communities are comparable in species richness, as well as in complementarity, with unique species being found at all second-growth sites
Summary
Southern Appalachian forests are dominated by second-growth vegetation following decades of intensive forestry and agricultural use, some old-growth patches remain. The southern Appalachian Mountains of eastern North America are home to an incredibly rich biota [1,2,3,4]. These mountains have been exposed and unglaciated for over 100 million years [5], much of their flora and fauna is ancient, and many groups have diversified extensively (e.g. amphibians reach their global peak diversity here [6]). In northern Appalachia, Chandler & colleagues [16, 17] compared species richness of litter-inhabiting beetles between old-growth and ~ 40 year old fragments, finding that beyond disappearance of a few old-growth specialists, overall species richness in second-growth forests was not seriously impacted. We recently examined similarity in species composition across the litter beetle communities from a network of old-growth and second-growth sites, scattered across western North Carolina and upstate South Carolina [21]; second-growth communities are comparable in species richness, as well as in complementarity, with unique species being found at all second-growth sites
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