Damselfly (Odonata: Calopterygidae) Population Decline in an Urbanizing Watershed

Abstract

Reduction of terrestrial vegetation and degradation of water quality are among the factors driving insect population decline in growing cities. In this study, we investigated the extent of habitat deterioration, behavioral and physiological responses, and fitness of a damselfly [Hetaerina americana (F.)] population in a semitropical region in central Mexico. The study population was located in a riverine area that crosses a small urban area (Tehuixtla city). We related two habitat variables (tree/shrub covered area and numbers of wastewater outlets) to presumable damselfly responses (larval and adult abundance, duration of adults exposed directly to sunlight, lipid content and muscle mass, and egg survival) over the years 2002 and 2016. We detected a reduction in terrestrial vegetation cover, an increase in wastewater outlets, and a decrease in larval and adult abundance. Adults were more exposed to sunlight in 2016 than in 2002 and showed a reduced lipid content and muscle mass in 2016. Egg survival also decreased. Although correlative, these results suggest impairment of damselfly condition (via lipid and muscle reduction) and fitness as urbanization increases.

Urban Areas Create Refugia for Odonates in a Semi-Arid Region

“…Damselflies, being smaller-bodied, have shorter development times, indicating that their greater measured prevalence at urban playas was due to factors other than duration of water availability, such as habitat structure or prey availability. Although damselfly abundance may be reduced at urban wetlands [ 51 ], our findings support those of Perron et al [ 9 ], who found greater damselfly diversity at urban stormwater ponds than at natural areas. This group of insects may be more tolerant of anthropogenic inputs, water quality, and habitat quality than previously considered.…”

Why do bugs perish? Range size and local vulnerability traits as surrogates of Odonata extinction risk

“…Our approach accepts some levels of uncertainty for individual species (e.g. a decrease in local abundance) [91], but at a large scale, it provides an estimate of extinction potential that is easy to replicate and that considers phylogenetic non-independence of extinction risk [3,92].…”

A global class reunion with multiple groups feasting on the declining insect smorgasbord

“…In the current era of defaunation 32 , many organisms are declining rapidly 12,15,16,[33][34][35][36][37] , and especially insects are suffering greatly 6,[8][9][10]13,18,38,39 . This is alarming because we know very little of the fundamental interactions between the majority of species.…”

“…Over the very last few decades, multiple studies have pointed to widespread decline among insects 7 . This pattern has been proposed to apply to both species-specific abundances and overall insect biomass and to extend across habitats with highly variable levels of human impact 6 – 11 , 13 , 18 . This is alarming, given the dominance of insects in terms of diversity 19 and biomass 20 , and the key role of insects in sustaining ecosystem processes and services 5 , 7 .…”

“…We wish to acknowledge the aforementioned prologue and to offer a complementary view to the biodiversity crisis around the planet. As the insects are declining, the insectivores are also in distress [12][13][14][15][16] . This leads to a notion that, instead of focusing solely on insects, we should simultaneously be studying interactions between insectivores and their prey 17 .…”