Search

Anthropogenically-driven environmental changes over the past two centuries have led to severe biodiversity loss, most prominently in the form of loss of populations and individuals. Better tools are needed to assess the magnitude of these wildlife population declines. Anecdotal evidence suggests European bat populations have suffered substantial declines in the past few centuries. However, there is little empirical evidence of these declines that can be used to put more recent population changes into historic context and set appropriate targets for species recovery. This study is a collaboration between academics and conservation practitioners to develop molecular approaches capable of providing quantitative evidence of historic population changes and their drivers that can inform the assessment of conservation status and conservation management. We generated a genomic dataset for the Western barbastelle, Barbastella barbastellus, a globally Near Threatened and regionally Vulnerable bat species, including colonies from across the species British and Iberian ranges. We used a combination of landscape genetics and approximate Bayesian computation model-based inference of demographic history to identify both evidence of population size changes and possible drivers of these changes. We found that levels of genetic diversity increased and inbreeding decreased with increasing broadleaf woodland cover around the colony location. Genetic connectivity was impeded by artificial lights and facilitated by the combination of rivers and broadleaf woodland cover. The demographic history analysis showed that both the northern and southern British barbastelle populations have declined by 99% over the past 330-548 years. These declines may have been triggered by loss of large oak trees and native woodlands due to shipbuilding during the early colonial period. Genomic approaches can be applied to provide a better understanding of the conservation status of threatened species, within historic and contemporary context, and inform their conservation management. This study shows how we can bridge the implementation gap and promote the application of genomics in conservation management through co-designing studies with conservation practitioners and co-developing applied management targets and recommendations.

Abstract Animals modify their behaviours and interactions in response to changing environments. In bats, environmental adaptations are reflected in echolocation signalling that is used for navigation, foraging and communication. However, the extent and drivers of echolocation plasticity are not fully understood, hindering our identification of bat species with ultrasonic detectors, particularly for cryptic species with similar echolocation calls. We used a combination of DNA barcoding, intensive trapping, roost and emergence surveys and acoustic recording to study a widespread European cryptic species complex (Pipistrellus pipistrellus and Pipistrellus pygmaeus) to investigate whether sibling bat species could exhibit extreme echolocation plasticity in response to certain environmental conditions or behaviours. We found that P. pygmaeus occupied the acoustic niche of their absent congeneric species, producing calls with P. pipistrellus’ characteristic structure and peak frequencies and resulting in false positive acoustic records of that species. Echolocation frequency was significantly affected by the density of bats and by maternity rearing stage, with lower frequency calls emitted when there was a high density of flying bats, and by mothers while juveniles were non-volant. During roost emergence, 29% of calls had peak frequencies typical of P. pipistrellus, with calls as low as 44 kHz, lower than ever documented. We show that automatic and manual call classifiers fail to account for echolocation plasticity, misidentifying P. pygmaeus as P. pipistrellus. Our study raises a vital limitation of using only acoustic sampling in areas with high densities of a single species of a cryptic species pair, with important implications for bat monitoring. Significance statement Ultrasonic acoustic detectors are widely used in bat research to establish species inventories and monitor species activity through identification of echolocation calls, enabling new methods to study and understand this elusive understudied group of nocturnal mammals. However, echolocation call signalling in bats is intrinsically different to that of other taxa, serving a main function of navigation and foraging. This study demonstrates an extreme level of plasticity, showing large variation in call frequency and structure in different situations. We showcase the difficulty and limitation in using acoustic sampling alone for bat monitoring and the complications of setting parameters for species identification for manual and automatic call classifiers. Our observations of call frequency variation correlated with density and absence of congenerics provide novel insights of behavioural echolocation plasticity in bats.

Accepted manuscript version, licensed CC BY-NC-ND 4.0. We face an increasing global food security challenge as the human population continues to grow across the globe. As agricultural production rises to keep up with food demand, so too does the expansion of crop detrimental pest species. Early detection can be crucial to control their damage and relies on the use of accurate and dependable techniques. We report the first record of rice water weevil (Lissorhoptrus oryzophilus) in the Iberian Peninsula. The distribution range expansion of this invasive rice pest weevil is confirmed through traditional sampling and through natural sampling by bats combined with DNA metabarcoding, a non-invasive technique with strong potential for early detection of pests in agricultural areas. Presence of rice water weevil was confirmed genetically from bat faecal samples collected from a Pipistrellus pygmaeus bat roost in the Ebro Delta (Catalonia, Spain). The known distribution of this rice pest, native to North America, now includes four of the top five rice-producing European countries. To date, the economic damage caused by this pest in Europe is minimal and concentrated in small areas, but chemical and agronomic controls are implemented to control their populations. The nature of this record highlights the potential of insectivorous bats as natural samplers to detect (and possibly control) pest species in crops. Further studies are required to determine the full extent of the rice water weevil's spread, and to investigate integrated pest management systems, including biological control to suppress their populations.