Using DNA metabarcoding to explore spatial variation in diet across European Hawfinch populations

Abstract

The investigation of diet in avian species is essential for understanding their ecology and local adaptations, as well as long-term conservation. This can be particularly challenging because of the wide distribution and high ecological plasticity of many bird species. Here, we focused on the Hawfinch (Coccothraustes coccothraustes), which has shown variation in population trends. Across Europe, central and eastern European populations are moderately declining while western European populations are moderately increasing. Ecological drivers behind these differing trends are still unknown; one possibility is differences in diet, yet little research has been conducted into Hawfinch diet in mainland Europe or elsewhere. Dietary richness and variation are under-studied in woodland bird species, due primarily to challenges in accurately identifying plant and invertebrate taxa consumed. This study presents the first molecular dietary analysis of Hawfinch populations across two European countries. Faecal samples were collected between January and July of 2019 from Hawfinch caught at six artificial feed sites: two in Denmark and four in Germany. We successfully extracted DNA from 80 samples by amplifying plant Internal Transcribed Spacer 2 (ITS2) and invertebrate Cytochrome Oxidase Subunit 1 (COI) barcodes. A total of 35 plant and 37 invertebrate taxa were found, with plant and insect orders Fagales and Lepidoptera, respectively, the most frequently detected. Hawfinch dietary composition differed significantly between European countries, suggesting Hawfinch can make use of available food resources that are likely to differ spatially. Our study shows how DNA metabarcoding can be used to provide novel ecological information associated with under-studied bird species, thus providing essential information for future management and conservation of Hawfinch and their habitats.RESUMEN. El estudio de la dieta en especies de aves es esencial para entender su ecología y adaptaciones locales, así como su conservación a largo plazo. Esto puede ser particularmente difícil por las amplias distribuciones y la alta plasticidad ecológica que muestran varias especies de aves. Aquí nos enfocamos en Coccothraustes coccothraustes la cuál ha mostrado variación en tendencias poblacionales. A lo largo de Europa, las poblaciones del centro y del este están disminuyendo moderadamente mientras que las poblaciones del oeste están incrementando moderadamente. Los factores ecológicos detrás de esta diferencia en las tendencias son desconocidos hasta el momento; una posibilidad es la diferencia en la dieta, pero hay poca investigación en la dieta de C. coccthraustes en Europa continental o en cualquier otro lugar. La riqueza en la dieta y su variación ha sido poco estudiada en especies de aves de bosque, principalmente debido a retos relacionados con la correcta identificación de plantas e invertebrados consumidos. Este estudio presenta el primer análisis molecular de la dieta de las poblaciones de C. coccothraustes a lo largo de dos países europeos. Mu...