Revisiting the Evolution of Jamaican Anoles

An illustration from Gosse (1851) depicting Jamaica’s crown-giant, Anolis garmani (notice that Gosse used the outdated title, “Dactyloa Edwardsii”), adjoining to a West Indian boid (Chilabothrus).

Jamaica’s six endemic Anolis species–A. garmaniA. reconditusA. valencienniA. lineatopusA. grahami, and A. opalinus–have lengthy captured the fascination of Caribbean naturalists. And the way may they not? Though solely six, these lizards are among the many Caribbean’s most eye-grabbing. Take it from Phillip Henry Gosse, who recounted his expertise catching one among these six species utilizing a twine lasso in A Naturalist’s Sojourn in Jamaica (1851):

“The mode wherein I fashioned an acquaintance with the species could also be worthy of being associated. In the future in February, having ascended the ridge with a companion, my consideration was arrested by a Lizard a couple of foot lengthy, and of a energetic inexperienced color, on the trunk of a small tree, head downward, intently watching our motions as we stood close to. My younger pal recommended the opportunity of capturing it by slipping a noose over its head, whereas its consideration was engaged by whistling. I laughingly proceeded to strive the spell; and having made a noose of small twine, which I tied to the top of a change, I gently walked in the direction of him, whistling a energetic tune. To my astonishment he allowed me to slide the noose over his head, merely glancing his shiny eye on the string because it handed. I jerked the change; the music ceased; and the green-coated forester was sprawling within the air, dangling, tremendously to his annoyance, on the finish of my string. He was very savage, biting at each factor close to; presently his color started to vary from inexperienced to blackish, until it was of an uniform bluish black with darker bands on the physique, and a brownish black on the tail: the one hint of inexperienced.”

Since Gosse’s work on West Indian reptiles (together with formal designation of the Jamaican anole radiation as Placopsis), a lot has modified in our understanding of Jamaica’s Anolis variety and evolution. In 2002, Todd Jackman and colleagues printed a research aiming to estimate the phylogenetic relationships amongst Jamaica’s anoles.

The authors discovered help for the next topology (Jackman et al. 2002; Fig. 7): A. lineaotopus and A. reconditus type a clade that’s sister to the remaining Jamaican anoles, adopted by A. valencienni, A. garmani, and, finally, A. grahami A. opalinus. Jackman et al. would proceed in the identical paper to debate phylogeography and intraspecific divergences. Notably, a single A. opalinus from Hardwar Hole (Blue Mountains) gave the impression to be extra intently allied to A. valencienni than to different sampled A. opalinus people. This numerous array of mitochondrial haplotypes recovered from A. opalinus then raises the query, does the historical past of Anolis on Jamaica contain hybridization, or is it merely a results of incomplete lineage sorting we could anticipate from a speedy adaptive radiation?

Practically twenty years glided by with out a solution. Was the phylogenetic speculation posited by Jackman et al. appropriate? What’s happening with A. opalinus? Individually, within the twenty years for the reason that work by Jackman and colleagues, a revolution has occurred in phylogenetic biology. Within the research of phylogeny, if introgression (e.g., historic mitochondrial seize on account of hybridization) has performed a job in shaping the evolutionary historical past of the related group, it’s vital that we check if such occasions have occurred, and subsequently be capable of disentangle and finally account for them in our phylogenetic estimations. Failure to take action can result in deceptive topologies, inaccurate reconstructions of evolutionary histories and parameter estimates, in addition to shortcomings in precisely describing and recognizing biodiversity.

Fortunately, decision to this challenge has been afforded by a number of of us (Claudia Solís-Lemus and Cécile Ané, to call simply two) who’ve developed statistical strategies to detect and account for each incomplete lineage sorting (ILS) and reticulate patterns of evolution (introgression). So, how does this relate to these oh-so-cool Jamaican anoles? That is the place Myers et al. (2021) are available in.

In a brand new research within the Highlight part of Systematic Biology, Myers and colleagues re-open the investigation into Jamaican Anolis phylogeny utilizing the aforementioned suite of novel strategies. For these in attendance on the Joint Assembly of Herpetologists and Ichthyologists in 2018, the early phases of this work have been offered by college students conducting analysis on the American Museum of Pure Historical past, beforehand featured on Anole Annals. Utilizing genotyping-by-sequencing (an method that has been utilized elsewhere in Anolis analysis), the authors generate swaths of SNP information from the nuclear genome. To be precise, the whole dataset comprised 257,317 base pairs (simply over 2,900 loci). Restriction-site-associated approaches (i.e., RAD-Seq) to sequencing DNA have made it possible to seize giant, consultant samples of the nuclear genome at low value.

Armed with information from each the nuclear and mitochondrial genomes, Myers et al. (2021) discovered dramatically totally different relationships and evolutionary histories amongst species between the 2 sources. Determine 3 demonstrates this disparity properly, and additional hammers residence the final risks of violating mannequin assumptions in phylogenetic inference (on this case, the multi-species coalescent [MSC] mannequin, which assumes a scarcity of gene circulation amongst sampled taxa).

First, when utilizing solely the mtDNA information in a MSC framework, the authors discover A. opalinus from the Blue Mountains to be polyphyletic, a consequence concordant with the inference of Jackman et al. (2002). Particularly, one A. opalinus lineage (Blue Mountains) is sister to A. valencienni, whereas the opposite A. opalinus lineage is sister to A. grahami. Notably, the time calibrated mtDNA gene-tree suggests the 2 A. opalinus mtDNA genomes are greater than 30 million years divergent!

The authors then infer a species tree utilizing the GBS information in an MSC framework (one which assumes gene-tree species-tree discordance may be attributed to incomplete lineage sorting and accounts for such). With this tree, the 2 A. opalinus lineages type a clade sister to A. grahami and A. garmani. Lastly, with SnaQ (a modeling program developed by Solís-Lemus and colleagues to deduce reticulation occasions throughout a tree), the authors recovered an similar topology to the nuclear DNA primarily based species-tree, however with excessive help for a single introgression occasion (and therefore, reticulate evolution) between A. opalinus and A. grahami. Utilizing simulations, Myers and colleagues present proof towards ILS because the causative agent for gene-tree species-tree discordance, favoring hybridization because the offender.

I gained’t spoil the Dialogue, however a lot of Jamaican Anolis evolution stays open-ended (together with the position of adaptive introgression in shaping Anolis communities). It’s in all probability secure to say Gosse wasn’t pondering the opportunity of adaptive introgression in shaping Jamaican Anolis phylogeny. Nonetheless, decision of the excellent questions recognized by Myers et al. (2021) will come primarily by means of Gosse’s philosophy–getting out within the area, catching lizards, and getting a more-fine scale, phylogeographic image of the variation over area and time in Jamaican Anolis.

I thank Ed Myers and Kevin de Queiroz for suggestions on this weblog publish.

Literature Cited:

Jackman, T. R., Irschick, D. J., De Queiroz, Okay., Losos, J. B., & Larson, A. 2002. Molecular phylogenetic perspective on evolution of lizards of the Anolis grahami collection. Journal of Experimental Zoology 294(1) 1-16.

New literature alert!


Interspecific Gene Move and Mitochondrial Genome Seize Throughout the Radiation of Jamaican Anolis Lizards (Squamata; Iguanidae)


In Systematic Biology

Myers, Mulcahy, Falk, Johnson, Carbi, de Queiroz

Gene circulation and reticulation are more and more acknowledged as vital processes within the diversification of many taxonomic teams. With the growing ease of gathering genomic information and the event of multispecies coalescent community approaches, such reticulations may be accounted for when inferring phylogeny and diversification. Caribbean Anolis lizards are a traditional instance of an adaptive radiation wherein species have independently radiated on the islands of the Higher Antilles into the identical ecomorph lessons. Throughout the Jamaican radiation no less than one species, A. opalinus, has been documented to be polyphyletic in its mitochondrial DNA, which might be the results of an historic reticulation occasion or incomplete lineage sorting. Right here we generate mtDNA and genotyping-by-sequencing (GBS) information and implement gene-tree, species-tree, and multispecies coalescent community strategies to deduce the diversification of this group. Our mtDNA gene-tree recovers the identical relationships beforehand inferred for this group, which is strikingly totally different from the species-tree inferred from our GBS information. Posterior predictive simulations recommend that our genomic information violate generally adopted assumptions of the multispecies coalescent mannequin, so we use community approaches to deduce phylogenetic relationships. The inferred community topology incorporates a reticulation occasion however doesn’t clarify the mtDNA polyphyly noticed on this group, nevertheless coalescent simulations recommend that the noticed mtDNA topology is probably going the results of previous introgression. How frequent a signature of gene circulation and reticulation is throughout the radiation of Anolis is unknown; nevertheless, the reticulation occasions that we show right here could have allowed for adaptive evolution, as has been recommended in different, newer adaptive radiations.

Aryeh Miller
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