Wed, Aug 04, 2021:On Demand
Background/Question/Methods Species, landscape, and patch traits influence the persistence of species within and movement of individuals between habitat patches in fragmented landscapes. However, while species and landscape characteristics have received a lot of attention, patch characteristics such as area, perimeter-area ratio, and shape are mainly studied for their effects on persistence within patches and not for their role in movement. In this study, we investigated how these three patch traits influence persistence and movement in beetles (Order: Coleoptera), bees (Clade: Anthophila), and thrips (Order: Thysanoptera) - three taxa that vary in their resource requirements and dispersal abilities. We sampled insect communities in experimental glades and the adjacent forest matrix at Washington University in St. Louis' Tyson Research Center using flight-intercept traps. These patches are one of two shapes (circle and star), two areas, and two perimeter-area ratios, allowing us to isolate the effects of area, perimeter-area ratio, and shape. We collected insects and quantified habitat characteristics over two one-week periods in June 2018 and 2019.
Results/Conclusions We found that site type affected the similarity of beetle communities within glades compared to those in the forest. Specifically, the Jaccard index values were higher for large-circle than large-star patches (same area; different shape and perimeter-area ratio). We did not detect a difference between large- and medium-circle patches (same shape; different area and perimeter-area ratio) nor between large-star and medium-circle patches (same perimeter-area ratio; different shape and area). Bees, which rely on glades for food resources and have strong dispersal abilities, displayed increased persistence and movement with a more complex patch shape that simultaneously maximized area and perimeter-area ratio. The thrips collected in this study were primarily herbaceous plant feeders and poor dispersers. While we did not detect much movement of thrips, their persistence within patches was associated with higher perimeter-area ratios, irrespective of patch area or shape. The observed effects on insect communities do not appear to be mediated by changes in vertical plant structure or plant resource density. Taken together, this work demonstrates the importance of individual patch traits varies across insect taxa. Conservation activities in fragmented landscapes that change patch traits should evaluate the potential impacts on target and non-target species to avoid simultaneously improving conditions for beneficial (e.g., bees) and pestiferous (e.g., thrips) insects.
Results/Conclusions We found that site type affected the similarity of beetle communities within glades compared to those in the forest. Specifically, the Jaccard index values were higher for large-circle than large-star patches (same area; different shape and perimeter-area ratio). We did not detect a difference between large- and medium-circle patches (same shape; different area and perimeter-area ratio) nor between large-star and medium-circle patches (same perimeter-area ratio; different shape and area). Bees, which rely on glades for food resources and have strong dispersal abilities, displayed increased persistence and movement with a more complex patch shape that simultaneously maximized area and perimeter-area ratio. The thrips collected in this study were primarily herbaceous plant feeders and poor dispersers. While we did not detect much movement of thrips, their persistence within patches was associated with higher perimeter-area ratios, irrespective of patch area or shape. The observed effects on insect communities do not appear to be mediated by changes in vertical plant structure or plant resource density. Taken together, this work demonstrates the importance of individual patch traits varies across insect taxa. Conservation activities in fragmented landscapes that change patch traits should evaluate the potential impacts on target and non-target species to avoid simultaneously improving conditions for beneficial (e.g., bees) and pestiferous (e.g., thrips) insects.