aDNA -sequencing a very old lizard holotype

Draco punctatus Photo by Jimmy A. McGuire. From Figure 1 in McGuire et al. 2018

Sometimes taxonomic issues can be intractable without genetic data, yet since old herp holotypes have been formalin-fixed or preserved in ethanol for long periods if time, they generally have highly degraded DNA, thus getting those genetic data can be extremely difficult.  Case in point, earlier this year I was part of a publication lead by Jim McGuire that attempted to sequence DNA from the 145 year old holotype of Draco cristatellus. This involved a ton of effort to get DNA from this specimen and then to get sequence from this extract. Read the article to see the extent of work that went into recovering those data from this very old specimen, but in a nutshell we tried a bunch of extraction techniques, and the only thing that worked for extraction was an aDNA protocol. We followed that up with a bunch of NGS sequencing, and  recovered a small amount of sequence data -but SUCCESS!!

Why does it matter? Often the reason that these genetic data are needed is to resolve a taxonomic issue.  If a species name and type exists but you have two or more unique lineages to which the name could apply, and morphological characters are difficult or impossible to discern based on the type specimen, then without genetic data, assignment of a name to the correct lineage is not straight forward. Genetic data may represent the only way to resolve some of these issues, as was certainly the case for these lizards.

Here is the citation and link to the open access article, so enjoy!

McGuire JA, Cotoras DD, O’Connell B, Lawalata SZS, Wang-Claypool CY, Stubbs A, Huang X, Wogan GOU, Hykin SM, Reilly SB, Bi K, Riyanto A, Arida E, Smith LL, Milne H, Streicher JW, Iskandar DT. (2018) Squeezing water from a stone: high-throughput sequencing from a 145-year old holotype resolves (barely) a cryptic species problem in flying lizards. PeerJ 6:e4470

Asian Spiny toads invade Wallacea

We just published a paper in Global Change Biology calling attention to the invasion of the Wallacea bioregion by the Asian spiny toad (Duttaphrynus melanostictus). While the invasion has been going on for several decades, it has been largely overlooked. The Wallacean  islands are naturally toad-free, which means that the native species (predators) are naive about the toxicity of the toads, and therefore, are at risk if they attempt to consume the poisonous toads. Of particular concern is the iconic apex predator, the Komodo Dragon, which is known to be susceptible to the toad toxins. While the toads have not reached the islands on which Komodo Dragons are found, they have reached all of the adjacent islands, suggesting that invasion is possible unless actions are taken to reduce introduce risk. Environmental niche models suggest that if the toads do reach those islands that the climate is suitable for them to establish themselves. We also found that all of the invading toads we tested from throughout Wallacea have the same haplotype and have been introduced from populations from the Sunda Shelf Islands of Java and Sumatra. This suggests that local ferries and boats are transporting the toads.

Here is the citation, and a link to the paper!

S. Reilly*, G. O. U. Wogan*, A. Stubbs, E. Arida, D. Iskandar, and J. McGuire. Toxic Toad Invasion of Wallacea: a Biodiversity Hotspot Characterized by Extraordinary Endemism. Global Change Biology (in press) early view link DOI: 10.1111/gcb.13877


Also we have had some nice coverage of this paper by Mongabay

Island-hopping toxic toad threatens iconic Komodo dragon

More on toad invasions

We just published a new paper on the invasion of the Spiny Asian toad (Duttaphrynus melanostictus) to Madagascar. This new paper expanded sampling of toads within their native Asian range as well as those introduced in Madagascar. The expanded sampling suggests that the introduction came from Southern Vietnam or Cambodia. We also did some niche modelling to assess the potential distribution of the toad within Madagascar. Anyway, check it out!

Figure 1. from Vences et al. 2017. Tracing a toad invasion: Lack of mitochondrial DNA variation, haplotype origins, and potential distribution of introduced Duttaphrynus melanostictus in Madagascar. Amphibia-Reptilia v. 38: 197-207 DOI:10.1163/15685381-00003104