Underrepresentation of dietary specialist larval Lepidoptera in small forest fragments: Testing alternative mechanisms

Growing evidence suggests that organisms with narrow niche requirements are particularly disadvantaged in small habitat patches, typical of fragmented landscapes. However, the mechanisms behind this relationship remain unclear. Dietary specialists may be particularly constrained by the availability of their food resources as habitat area shrinks. For herbivorous insects, host plants may be filtered out of small habitat fragments by neutral sampling processes and deterministic plant community shifts due to altered microclimates, edge effects, and browsing by ungulates. We examined the relationship between forest fragment area and the abundance of dietary-specialist and dietary-generalist larval Lepidoptera (caterpillars) and their host plants in the northeastern USA. We surveyed caterpillars and their host plants over three years in equal-sized plots within 32 forest fragments varying in area between 3 and 1014 ha. We tested whether the abundances and species richness of dietary speciali..., Data on abundances of moth caterpillars were collected from 32 forest fragments in eastern Connecticut USA in June of 2017 - 2019. At each site
1) Lepidopteran caterpillars were collected by beating branches over a white sheet within 12 25 m^2 plots.
2) Vegetation was sampled in 3 100 m^2 vegetation plots adjacent to the caterpillar plots.
3) Deer activity was assessed in the hectare centered on the caterpillar plots using a combination of pellet densities and browsing incidence on woody saplings within 25 1 m^2 plots at 20 m intervals and 5 camera traps (deployed at each site for 2 weeks during January - March 2018).
The files here provide the raw data on caterpillar counts within the 12 caterpillar plots and woody plant abundances within the 3 vegetation plots. 
Data were analyzed using generalized mixed effects models. Code is provided on GitHub (DOI: 10.5281/zenodo.14847790)., , # Underrepresentation of dietary specialist larval Lepidoptera in small forest fragments: testing alternative mechanisms

[https://doi.org/10.5061/dryad.k3j9kd5k8](https://doi.org/10.5061/dryad.k3j9kd5k8)

## Description of the data and file structure

Data were collected from 32 forest fragments of varying size (3 - 1014 ha) in Connecticut, USA. Within each fragment, we established:

1. 3 10 x 10 m vegetation sampling plots, arranged 25 apart on a triangle. All woody stems > 1 m tall were measured (diameter at breast height or height) and identified to species.
2.  4 5 x 5 m caterpillar sampling plots on the edges of each vegetation plot (12 total per site). These caterpillar plots were sampled for larval Lepidoptera during June of each year 2017 - 2019, by striking branches between 1 - 2 m tall within the plots.
3. Deer activity in the hectare surrounding the vegetation and caterpillar plots. We recorded pellet densities and proportion of browsed seedlings within 25 1 m^2^ plots on a ...