Digging in a 120 years-old lunch: What can we learn from collection specimens of extinct species?

Abstract

Studying collection specimens is often the only way to unravel information about recent extinctions. These can reveal knowledge on threats and life traits related to extinction, and contribute, by extrapolation, to the conservation of extant species. However, high-throughput sequencing methods have rarely been applied to extinct species to reveal information on their ecology. Insular species are especially prone to extinction. We studied the gut contents of three specimens of the extinct giant skink Chioninia coctei of the Cabo Verde Islands using microscopy and DNA-metabarcoding. The presence of Tachygonetria adult nematodes suggests plants as important diet items. Our metabarcoding approach also identified plants and, additionally, invertebrates, supporting the hypothesis of C. coctei’s generalist diet. The absence of vertebrates in the digestive contents may reflect the decline of seabirds on the Desertas Islands that could have contributed to the debilitation of the giant skink, already depleted by persecution and severe droughts. Even with a small sample size, this study contributes to shedding light on the trophic roles of this enigmatic extinct species and emphasizes the need to develop holistic conservation plans for island threatened taxa. Additionally, it illustrates the potential of integrating up-to-date molecular methods with traditional approaches to studying collection specimens to help to solve ecological puzzles in other ecosystems.

Islands, saurians and parasites

“…This recently extinct large saurian (Andreone Gavetti, 1998;Miralles et al, 2010) shows a particular teeth morphology that has been regarded by several authors as evidence of an adaptative shift towards herbivorous or omnivorous diet (Peracca, 1891;Pompanon et al, 2012). Our recent studies on collection specimens support the adaptation towards the consumption of plant matter by C. coctei, identifying both items of this nature in their digestive systems and a very wide helminth fauna of oxyurid nematodes typical of herbivorous tortoises (Pinho et al, 2022).…”

“…This was for example the cases of the species Gallotia simonyi (see Roca et al, 1999a), Gallotia bravoana (see Roca, 2012) and Plestiodon longirostris (see Roca García, 2021a). In the cases of Podarcis liolepis (see Roca, 2016) and Chioninia coctei (see Pinho et al, 2022) the few analysed specimens were museum specimens loaned for study with the pertinent permission.…”

“…The Cabo Verde archipelago also has a volcanic origin, and its colonization was probably from continental Africa and / or from the dispersion of species from other islands of the Macaronesian region. We were able to do the helminthological study only from five museum specimens (Pinho et al, 2022) of Chioninia coctei (Duméril et Bibron, 1839) (Sauria: Scincidae), a species considered extinct since the second half of the twentieth century (Pinho et al, 2022). It is an endemism that lived in some islands and islets of this archipelago located about 500 km from the African Atlantic coast and that together with the Canary Islands and other archipelagos of the eastern Atlantic form the region of Macaronesia (Mateo et al, 2022).…”

“…Island ecosystems present the highest rates of both unique biodiversity and species extinctions (Whittaker et al, 2017). Even though the number of species is typically low compared to the mainland, the number of endemics in islands is usually high (Whittaker et al, 2017;Pinho et al, 2022). On the other hand, low gene flow among islands, together with lower predation pressures and more limited food resources than in mainlands, promote the occurrence of unusual biological characteristics, such as diet specialization (Schluter, 1988;Pérez-Mellado Corti, 1993;Roca, 1999) and gigantism (Pregill, 1986;Greer, 2001).…”