Unraveling Reticulate Evolution in Opuntia (Cactaceae) From Southern Mexico

The process of hybridization occurs in approximately 40% of vascular plants, and this exchange of genetic material between non-conspecific individuals occurs unequally among plant lineages, being more frequent in certain groups such as Opuntia (Cactaceae). This genus is known for multiple taxonomic controversies due to widespread polyploidy and probable hybrid origin of several of its species. Southern Mexico species of this genus have been poorly studied despite their great diversity in regions such as the Tehuacán-Cuicatlán Valley which contains around 12% of recognized Mexico’s native Opuntia species. In this work, we focus on testing the hybrid status of two putative hybrids from this region, Opuntia tehuacana and Opuntia pilifera, and estimate if hybridization occurs among sampled southern opuntias using two newly identified nuclear intron markers to construct phylogenetic networks with HyDe and Dsuite and perform invariant analysis under the coalescent model with HyDe and Dsuite. For the test of hybrid origin in O. tehuacana, our results could not recover hybridization as proposed in the literature, but we found introgression into O. tehuacana individuals involving O. decumbens and O. huajuapensis. Regarding O. pilifera, we identified O. decumbens as probable parental species, supported by our analysis, which sustains the previous hybridization hypothesis between Nopalea and Basilares clades. Finally, we suggest new hybridization and introgression cases among southern Mexican species involving O. tehuantepecana and O. depressa as parental species of O. velutina and O. decumbens.

Genetic and morphological variation of Oxymycterus (Rodentia: Sigmodontinae) in the Brazilian Atlantic Forest

We present a new assessment of the genetic and morphological variation within Oxymycterus quaestor Thomas, 1903, which currently includes the junior synonyms O. judex Thomas, 1909 and O. misionalis Sanborn, 1931. We integrate distinct lines of evidence, including variation of mitochondrial (Cytochrome b [Cytb]) and nuclear (intron 7 of beta fibrinogen gene [Fgb]) sequences, and the assessment of skull quantitative traits based on geometric morphometrics, throughout the Atlantic Forest of Southeastern-Southern Brazil, Argentina, and Paraguay. Phylogenetic relationships based on Cytb indicate that O. quaestor is structured in four well-supported clades (lineages A–D), one of them (lineage C) including topotypes of a previously associated nominal form (O. judex). However, these Cytb lineages exhibit lower levels of differentiation based on the Fgb locus, and are not recovered in the genealogies of this nuclear marker, representing a case of mitonuclear discordance. The Cytb lineages also broadly overlapped in the morphospace both in skull shape and size, which sustain the current wider concept of O. quaestor as one single young species (0.947 Myr) that is recently expanding, and ultimately branching out, in the Atlantic Forest.

The taxonomic status of the Castelo dos Sonhos Hantavirus reservoir, Oligoryzomys utiaritensis Allen 1916 (Rodentia: Cricetidae: Sigmodontinae)

Species of the genus Oligoryzomys are commonly found accross Latin America, and several of them play important rolesas natural reservoirs of Hantaviruses. Here we demonstrate that O. utiaritensis, the natural reservoir of hantavirus Castelodos Sonhos in northwestwern Brazil and previously considered a junior synonym of O. nigripes or O. eliurus, is a validspecies. Morphology, morphometry, karyotyping, and phylogenetic reconstructions based on nuclear (intron 7 of the beta-fibrinogen gene) and mitochondrial (cytochrome b) DNA show that O. utiaritensis differs from O. nigripes and from otherforms of the genus, including the recently described taxon O. moojeni. Oligoryzomys utiaritensis differs in external (whit-ish ventral pelage and tail weakly bicolored) and cranial (incisive foramina never extending posteriorly the alveolus lineof M1) characters from sympatric species. It has the highest diploid number (2n=72) within Oligoryzomys, and is charac-terized by three putative synapomorphies in cytochrome b, and one in intron 7 of beta fibrinogen. We also point to theassignment of Oligoryzomys eliurus as a junior synonym of O. nigripes. Finally, we present phylogenetic analyses of in-trageneric relationships showing that O. utiaritensis is a member of a clade containing Amazonian and Cerrado taxa, including O. moojeni, O. rupestris, and O. delicatus.