The influence of chalk grasslands on butterfly phenology and ecology.

Matthew P Greenwell,Kevin Watts,Marc S Botham,David B Roy,Luke C Evans,John C Day,Michael W Bruford,Melanie Gibbs,Tom H Oliver,Ian Middlebrook

doi:10.1002/ece3.8111

Abstract

The influence of large‐scale variables such as climate change on phenology has received a great deal of research attention. However, local environmental factors also play a key role in determining the timing of species life cycles. Using the meadow brown butterfly Maniola jurtina as an example, we investigate how a specific habitat type, lowland calcareous grassland, can affect the timing of flight dates. Although protracted flight periods have previously been reported in populations on chalk grassland sites in the south of England, no attempt has yet been made to quantify this at a national level, or to assess links with population genetics and drought tolerance. Using data from 539 sites across the UK, these differences in phenology are quantified, and M. jurtina phenology is found to be strongly associated with both site geology and topography, independent of levels of abundance. Further investigation into aspects of M. jurtina ecology at a subset of sites finds no genetic structuring or drought tolerance associated with these same site conditions.

Highlights

We focus on how site-specific characteristics affect the phenology of the Lepidoptera Maniola jurtina (Figure 1), a species known to be affected by local site conditions, with protracted flight periods and occasional second peaks in emergence observed on chalk grasslands in the south of England (Goulson, 1993a; Thomas & Lewington, 2010)
We determined whether differences in other aspects of ecology were associated with the same landscape attributes
Positive, associations between the phenology of M. jurtina and geology and topography, that is, key flight dates are delayed with increasing chalk cover and slope angle

Summary

| INTRODUCTION

Changes in the phenology of Lepidoptera is a well-studied subject (Dell et al, 2005; Diamond et al, 2011; Hodgson et al, 2011; MacGregor et al, 2019; Roy et al, 2015; Roy & Sparks, 2000) in part because long-term monitoring data are available for a large number of species, allowing temporal changes in phenology to be measured (Roy & Sparks, 2000). The protracted flight period of M. jurtina on chalk grasslands in the UK has received previous investigation (Goulson, 1993a; Shreeve, 1989), no effort has yet been made to quantify these differences in phenology at the national scale Compared with landscapes such as farmland or woodland, chalk grasslands are warmer and drier during summer, resulting in more favorable conditions for thermophilic species (Mortimer et al, 1998). Clear genetic clustering of individuals into chalk and nonchalk populations would suggest a high level of genetic differentiation, which may support the idea of locally adapted races as an explanation for the differences in flight periods To explore these possibilities, we examine the flight periods of M. jurtina in the UK at 539 sites differing in geology and topography and quantify the variability in phenology. Are populations of M. jurtina on chalk grasslands more drought- tolerant than populations in other habitats?

| MATERIALS AND METHODS

Findings

| DISCUSSION