An evolutionary study of early diverging sedges (Carex subg. Psyllophorae) sheds light on a strikingly disjunct distribution in the Southern Hemisphere, emphasizing in its Patagonian diversification

GARCÍA-MORO, PABLO; LUCEÑO, MODESTO; OTERO, ANA; FORD, KERRY A.; JIMÉNEZ-MEJÍAS, PEDRO; BENÍTEZ-BENÍTEZ, CARMEN; DONADÍO, SABINA; MARTÍN-BRAVO, SANTIAGO

Toledo

Congreso; Primer Congreso Español de Botánica; 2021

Sociedad Botánica Española

Carex subgenus Psyllophorae is considered an engaging study group due to its early diversification (early Miocene), compared to most lineages of Carex, and its remarkable disjunct distribution in four different continents: Western Palearctic, Sub-Saharan Africa, SW Pacific and South America. In this last continent, section Junciformes is distributed in Patagonia and the Andes, where it is one of the few Carex groups with a significant in-situ radiation. To assess the role of historical geo-climatic events in the evolutionary history of the group, particularly intercontinental colonization events and diversification processes, with emphasis in South America.We perform an integrative study using phylogenetic (including four Sanger DNA regions), biogeographic, bioclimatic niche evolution, and diversification rate analyses in order to assess the evolutionary history of subg. Psyllophorae.The crown age of monophyletic subg. Psyllophorae was dated to early Miocene, which supports this lineage as one of the oldest within Carex. This age implies a diversification scenario away from primary tectonic vicariance hypotheses and suggests long-distance dispersal-mediated allopatric diversification in each of the four continents. The diversification rates underwent a slowdown over time in the whole subgenus. Section Junciformes remained in Northern Patagonia since its divergence until Plio-Pleistocene glaciations, which likely favoured multiple colonizations towards other South American regions. Andean orogeny appears to have acted as a northwards colonization corridor, which contrasts with the general pattern of North-to-South migration from the Northern Hemisphere. A direct long-distance dispersal event is inferred from South America to the Pacific SW. A striking niche conservatism characterizes the evolution of the entire clade.Geography seems to have played a primary role in the diversification of subg. Psyllophorae in general and sect. Junciformes in particular. Its relatively high speciesnumber in South America results from simple accumulation of morphological changes over time (disparification) since its early diversification, rather than shifts in ecological niche related to increased diversification rates (radiation). Section Junciformes underwent little ecological changes, including the species involved in the trans-Pacific disjunction, which implies the pre-adaptation of the group prior to the colonization of the Pacific SW.