Biology subjects

Perez-Escobar, O. A.

Publications and source records attributed to Perez-Escobar, O. A..

4 recordsLinked to original sources

bioRxiv2017

From tree tops to the ground: reversals to terrestrial habit in Galeandra orchids (Epidendroideae: Catasetinae)

The colonization of the epiphytic niche of tropical forest canopies played an important role in orchids extraordinary diversification in the Neotropics. However, reversals to the terrestrial habit occurred sparsely in species of Epidendroideae. To better understand which factors might have been involved in reversals to terrestrial habits in the predominantly epiphytic Epidendroideae, we investigate Galeandra diversification in time and space. We hypothesized that the reversal to the terrestrial habitat is linked to the origin of open vegetation habitats in South America. We generated a time-calibrated phylogeny based on a matrix of 17 out of 20 species of Galeandra plus outgroups and seven DNA markers. We found that Galeandra originated towards end of the Miocene, about 10 Ma in Amazonia (including the Guiana Shield). The terrestrial clade originated synchronously with the rise of dry vegetation biomes, suggesting that aridification during the last 5 million years dramatically impacted the diversification of epiphytic lineages in the Neotropics. Habit is correlated with floral spur lengths and geographic range size. The longer spurs and narrower ranges are found in epiphytic species: probably adapted to a specialized pollination mode, associated to the long-tongued Euglossini bees, which also prefer forested habits. The terrestrial species presents variable floral spurs and wide distribution ranges, with evidence of self-pollination, suggesting the loss of specialized pollination system and concomitant range expansion.

evolutionary biology↗

bioRxiv2017

Multiple Geographical Origins of Environmental Sex Determination enhanced the diversification of Darwins Favourite Orchids

Environmental sex determination (ESD) - a change in sexual function during an individual life span driven by environmental cues - is an exceedingly rare sexual system among angiosperms. Because ESD can directly affect reproduction success, it could influence diversification rate as compared with lineages that have alternative mating systems. Here we test this hypothesis using a solid phylogenetic framework of Neotropical Catasetinae, the angiosperm lineage richest in taxa with ESD. We assess whether gains of ESD are associated with higher diversification rates compared to lineages with alternative systems while considering additional traits known to positively affect diversification rates in orchids. We found that ESD has evolved asynchronously three times during the last ~5 Myr. Lineages with ESD have consistently higher diversification rates than related lineages with other sexual systems. Habitat fragmentation due to mega-wetlands extinction, and climate instability are suggested as the driving forces for ESD evolution.

evolutionary biology↗

bioRxiv2017

Recent origin of Neotropical orchids in the world’s richest plant biodiversity hotspot

* The Andean mountains of South America are the most species-rich biodiversity hotspot worldwide with about 15% of the worlds plant species, in only 1% of the worlds land surface. Orchids are a key element of the Andean flora, and one of the most prominent components of the Neotropical epiphyte diversity, yet very little is known about their origin and diversification.\n\n* We address this knowledge gap by inferring the biogeographical history and evolutionary dynamics of the two largest Neotropical orchid groups (Cymbidieae and Pleurothallidinae), using two unparalleled, densely-sampled orchid phylogenies (including 400+ newly generated DNA sequences), comparative phylogenetic methods, geological and biological datasets.\n\n* We find that the majority of Andean orchid lineages only originated in the last 15 million years. Most Andean lineages are derived from lowland Amazonian ancestors, with additional contributions from Central America and the Antilles. Species diversification is correlated with Andean orogeny, and multiple migrations and re-colonizations across the Andes indicate that mountains do not constrain orchid dispersal over long timescales.\n\n* Our study sheds new light on the timing and geography of a major Neotropical radiation, and suggests that mountain uplift promotes species diversification across all elevational zones.

evolutionary biology↗

bioRxiv2017

The improbable journeys of epiphytic plants across the Andes: Historical biogeography of Cycnoches (Catasetinae, Orchidaceae)

The Andean uplift is one of the major orographic events in the New World and has impacted considerably the diversification of numerous Neotropical organisms. Despite its importance for biogeography, the specific role of mountain ranges as a dispersal barrier between South and Central American lowland plant lineages is still poorly understood. The swan orchids (Cycnoches) comprise ca 34 epiphytic species distributed in lowland and pre-montane forests of Central and South America. Here, we study the historical biogeography of Cycnoches to better understand the impact of the Andean uplift on the diversification of Neotropical lowland plant lineages. Using novel molecular sequences (five nuclear and plastid regions) and twelve biogeographic models with and without founder-event speciation, we infer that the most recent common ancestor of Cycnoches may have originated in Amazonia ca 5 Mya. The first colonization of Central America occurred from a direct migration event from Amazonia, and multiple bidirectional trans-Andean migrations between Amazonia and Central America took place subsequently. Notably, such biological exchange occurred well after major mountain building periods. The Andes have not acted as an impassable barrier for epiphytic lowland lineages such as orchids having a great potential for effortless dispersal because of the very light, anemochorous seeds.

evolutionary biology↗