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Members of the Crotalus durissus species group are amongst the largest species of rattlesnakes and are of strong medical importance. The taxonomy of the group is convoluted, and the line of what is considered a species, subspecies or populations is hard to define. A recent study split one of the members of the group (C. culminatus) into three species, the nominal species, as well as C. ehecatl and C. mictlantecuhtli, based on genetic and morphological data. Here we reanalyze previously published mitochondrial and nuclear data, as well as additional sequences for two mitochondrial genes from members of the Crotalus durissus group, to test if isolation by distance (and not speciation) could be responsible for the genetic variation observed in previous studies. Our results show that the genetic differences between some of the species in the group (Crotalus simus – C. durissus and C. culminatus – C. ehecatl) are lower than intra-specific genetic distances. The only nuclear gene at hand for the C. durissus group (oocyte maturation factor Mos, c-mos) is not phylogenetically informative and cannot distinguish between many of the species in the genus, thus it is of little support when it comes to taxonomic decisions. We find low divergence at the mitochondrial level between these two species pairs, and at least in one of the species pairs we find a pattern of isolation-by-distance (IBD). Additionally, we performed a newly developed species delimitation analysis, DELINEATE, which supports the validity of C. mictlantecuhtli, but not C. ehecatl. These results suggest that the molecular differences at the mitochondrial level in members of the Crotalus durissus species group could be the result of IBD and not necessarily due to speciation events. We believe that additional sampling as well as additional molecular data is necessary to clarify species limits in the Crotalus durissus species group.

The herpetofauna of Colima has received relatively little attention until recently. A few state lists and several unpublished dissertations are the only references available for the herpetofauna of the state. Recently a revised herpetofaunal state list was published by Lemos-Espinal et al. (2020). Unfortunately, that revision was published with numerous errors and omissions. Here we review all published accounts on the herpetofauna of Colima as well as two unpublished thesis related to the herpetofauna of the state, and records in online databases (GBIF, Vertnet). We examine museum specimens of previously published taxa and show that many of the species reported from the state are in fact misidentifications, and that other species already known from the state have been ignored in the most recent state list. Additionally we report on six species of amphibians and reptiles that are new records for the state. Based on our revision, we show that the herpetofauna of Colima consists of 148  species, of which 110 are reptiles and 38 are amphibians, with five introduced species.  We also comment on species of possible occurrence in the state. We recommend that other state lists which have been published for Mexico be revised in order to fix a variety of issues and erroneous information in those lists.

Phylogenetic comparative studies suggest that the direction of deviation from bilateral symmetry (sidedness) might evolve through genetic assimilation; however, the changes in sidedness inheritance remain largely unknown. We investigated the evolution of genital asymmetry in fish of the family Anablepidae, in which males' intromittent organ (the gonopodium, a modified anal fin) bends asymmetrically to the left or the right. In most species, males show a 1 : 1 ratio of left-to-right-sided gonopodia. However, we found that in three species left-sided males are significantly more abundant than right-sided ones. We mapped sidedness onto a new molecular phylogeny, finding that this left-sided bias likely evolved independently three times. Our breeding experiment in a species with an excess of left-sided males showed that sires produced more left-sided offspring independently of their own sidedness. We propose that sidedness might be inherited as a threshold trait, with different thresholds across species. This resolves the apparent paradox that, while there is evidence for the evolution of sidedness, commonly there is a lack of support for its heritability and no response to artificial selection. Focusing on the heritability of the left : right ratio of offspring, rather than on individual sidedness, is key for understanding how the direction of asymmetry becomes genetically assimilated.

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