DNA barcoding of frugivorous bird diets

Eurasian Blackcap (Sylvia atricapilla)

Frugivores are critical components of restoration programs because they are seed dispersers. Thus, knowledge about bird–plant trophic relationships is essential in the evaluation of the efficacy of restoration processes. 

The traditional approach to the analysis of the diet of frugivore birds is the morphological identification of plant residues in droppings. Unfortunately, this is time-consuming, requires expert botanical knowledge, and cannot be used for fragments lacking any visible morphological characteristics. It seems obvious that molecular approaches such as DNA barcoding could instead be used as a universal tool to rapidly characterize the diet of a frugivorous bird or any other bird for that matter.

A group of Italian researchers was interested in using frugivorous birds as bioindicators of the efficacy of restoration at a site of community importance in Italy (Pusiano Lake in the North of the country). Over 3 years the team collected 642 Eurasian Blackcap (Sylvia atricapilla) droppings at the site during the autumn migration. Intact seeds and fragmented plant material were analyzed at two plastid loci (the barcode region rbcL and trnH-psbA), and the resulting plant identifications were validated by comparison with a reference molecular data set of the local flora.

The colleagues were able to find at least 17 plant species, including 7 of 11 newly transplanted taxa. Remarkably, 188 samples contained exclusively fragmented plant material unidentifiable with morphological methods. On the other hand it wasn't difficult to find sufficient DNA in all of their samples which shows the superiority of the method. Identification success was also exceptionally high which led to the summary:

Our results demonstrate the potential for DNA barcoding to be used to monitor the effectiveness of restoration plantings and to obtain information about fruit consumption and dispersal of invasive or unexpected plant species. Such an approach provides valuable information that could be used to study local plant biodiversity and to survey its evolution over time.