Biology subjects

Bahechar, I. A.

Publications and source records attributed to Bahechar, I. A..

2 recordsLinked to original sources

bioRxiv2021

Western Amazon was a center of Neotropical fish dispersal, as evidenced by the continental-wide time-stratified biogeographic analysis of the hyper-diverse Hypostomus catfish

The Amazon is probably the most diverse realm on Earth, and is considered to be the primary source of diversity and a center of dispersal for Neotropical terrestrial organisms. Yet, the assumption that the Amazon basin is a primordial place of fish species origination and dispersal into other drainages still need to be tested. We addressed this issue by inferring a time-stratified biogeographic history and reconstructing the ancestral habitat preference of Hypostomus, a continentally widespread and species-rich Neotropical genus. We found that Hypostomus emerged in the Western Amazon ([~]14.7 Ma), when the Western Amazon River was flowing northwards and disconnected from the Eastern Amazon. We show that dispersal events in the first half of Hypostomus evolution occurred from the Western Amazon into adjacent basins, initiating its Neotropical radiation. The ancestral preferred habitat consisted in small rivers with running waters, a predominant habitat in river headwaters. Because of strong niche conservatism in the early evolution of Hypostomus, we suggest that most of the out-of-Western-Amazon dispersal occurred via headwater captures. The radiation of Hypostomus was further promoted by major reconfigurations of river basins, which opened dispersal opportunities into new drainages. Diversification in habitat preference coincided with colonization of basins already occupied by congenerics, indicative of niche shifts triggered by inter-specific competition and species coexistence. By analyzing the evolutionary history of Hypostomus, we show that Western Amazon was the main center of fish dispersal in the Neotropical Region from Middle Miocene to the present, supporting the cradle hypothesis of fish origination and dispersal.

evolutionary biology↗

bioRxiv2021

Loricarioid catfish evolved skin denticles that recapitulate teeth at the structural, developmental, and genetic levels

The first vertebrate mineralized skeleton was an external bony armor coated with dental structures. The subsequent emergence of a mineralized endoskeleton and of teeth are considered key innovations in the diversification of vertebrates. Although time clouds our understanding of the initial evolution of these mineralized structures, recent re-emergences may shed light on the underlying processes. Loricarioid catfishes are a lineage that, much like the ancestral vertebrates, bear denticle-clad bony armor from head to tail. Loricarioid denticles (LDs) and oral teeth are very similar in superstructure. We show here that other extra-oral dental structures are found as ancestral characters only in lineages that are distantly related to loricarioids such as sharks or coelacanth, indicating that LDs have independently re-emerged in loricarioid catfishes. We investigate whether the similarities between LDs and teeth extend to their developmental and genetic context, and how their development compares to that of other vertebrate integument structures. Our detailed study of the development of LDs, and gene expression analyses through in situ hybridization confirm that all 12 genes from the tooth-forming gene regulatory network (oGRN) are expressed in developing LDs in a similar way as they are expressed in developing teeth. We then compare the developmental, structural, and genetic aspects of LD and teeth with that of other integument appendages such as fish scales, shark dermal denticles, feathers and hairs. We find that LDs share all developmental cues with teeth and, to a lesser extent, with the other vertebrate integument structures. Taken together, our results indicate that denticles have re-emerged on the trunk of loricarioid catfishes through the ectopic co-option of the oGRN rather than the resurrection of an ancestral trunk-specific denticle genetic pathway.

evolutionary biology↗