Historical changes in grassland area determined the demography of semi-natural grassland butterflies in Japan

Abstract

Semi-natural grassland areas expanded worldwide several thousand years ago following an increase in anthropogenic activities. However, semi-natural grassland habitat areas have been declining in recent decades due to changes in landuse, which have caused a loss of grassland biodiversity. Reconstructing historical and recent demographic changes in semi-natural grassland species will help clarify the factors affecting their population decline. Here we quantified past and recent demographic histories of Melitaea ambigua (Lepidoptera; Nymphalidae), an endangered grassland butterfly species in Japan. We examined changes in demography over the past 10,000 years based on 1378 bp of mitochondrial COI gene. We then examined changes in its genetic diversity and structure during the last 30 years using nine microsatellite DNA markers. The effective population size of M. ambigua increased about 3000-6000 years ago. In contrast, the genetic diversity and effective population sizes of many populations significantly declined from the 1980s to 2010s, which is consistent with a recent decline in the species population size. Our data suggest that the M. ambigua demography can be traced to changes in area covered by semi-natural grasslands throughout the Holocene.

Methods for retaining well-preserved DNA with dried specimens of insects

“…Many previous studies show that immersion of specimens in preservatives, such as, ethanol and propylene glycol preserve long fragments of DNA, whereas DNA in dried specimens rapidly degrades (Quicke et al, 1999;Vink et al, 2005;Hebert et al, 2013). Although dry specimens of insects, which contain only degraded DNA, have been widely used in genetic analyses, these analyses are much more diffi cult than when using fresh samples (Wandeler et al, 2007;Hebert et al, 2013;Nakahama et al, 2018). Although immersion in ethanol or propylene glycol may be appropriate for preserving long fragments of DNA, dried insects are more appropriate for morphological observations.…”

“…Insect specimens contain valuable genetic information (Wandeler et al, 2007;Tin et al, 2014;Nakahama et al, 2018). Such information is being used in applied entomology, conservation genetics and taxonomy, and reveals the history of the DNA sequences (Tin et al, 2014;Hausmann et al, 2016;Haran et al, 2018;Nakahama et al, 2018). However, there were very few studies on genetic information obtained from dried specimens of insects before the 2000s, because the rapid degradation of DNA in dried specimens of insects renders them unsuitable for genetic analyses (Wandeler et al, 2007;Nakahama & Isagi, 2017).…”

Integrative taxonomy and analysis of species richness patterns of nocturnal Darwin wasps of the genus Enicospilus Stephens (Hymenoptera, Ichneumonidae, Ophioninae) in Japan

“…Biodiversity is threatened with decline or loss in many environments. For instance, grasslands and marshes are declining by a progression of plant succession, sometimes due to changes in human land use, and in Japanese forests, over-browsing by a population explosion of deer frequently results in a bare forest floor; thus, many insects found there, including parasitoid wasps, are declining and threatened with extinction (e.g., Takatsuki 2009;Sakata and Yamasaki 2015;Nakahama et al 2018Nakahama et al , 2020. To conserve such insects, we have to gather information on their diversity and distribution, as well as their ecology.…”

Butterfly Conservation in China: From Science to Action

“…Population genetic research of endangered, endemic, and protected butterflies should be encouraged by forestry or environmental protection authorities on a regular basis or established as a component of standardized research packages in the conservation projects of those species. Quantifying population structure would benefit determining how management strategies, population histories (via monitoring data), and/or environments influence patterns of diversity [ 118 , 119 , 120 , 121 , 122 , 123 , 124 , 125 , 126 ]. Also, identifying levels and directions of gene flow and the number of private alleles in populations can provide critical information for a more effective conservation strategy in terms of increasing fitness [ 121 , 127 , 128 , 129 , 130 , 131 , 132 ].…”