The effects of incident microclimatic and soil parameters on the population sizes of selected tiger beetle species in Sri Lanka

Abstract

The population sizes of tiger beetles are known to display fluctuations in response to several microclimatic and soil parameters. In this study, analytical models were developed using negative binomial regression to describe the effects of weather and soil parameters on the population count of selected tiger beetle species. The tiger beetle species Hypaetha biramosa was selected to represent the coastal habitats and Ifasina labioaenea represented crop cultivated habitats. Population sizes for each tiger beetle species were estimated by taking counts maximum of two times a month using visual encounter surveys. Three sites were selected for each species. At each site, weather and soil parameters were measured. Based on the statistical models, an increase in wind speed was associated significantly with the decline in the counts of H. biramosa in the study sites. Solar radiation and soil electric conductivity were associated with an increase in the count of H. biramosa. An increase in the soil salinity and air temperature was associated positively with the increase of the counts of I. labioaenea in the study sites. The understanding of the effects of these parameters can be used to design better monitoring and conservation plans for Sri Lankan tiger beetles.