An Evolutionary Study of Carex Subg. Psyllophorae (Cyperaceae) Sheds Light on a Strikingly Disjunct Distribution in the Southern Hemisphere, With Emphasis on Its Patagonian Diversification

Abstract

Carex subgenus Psyllophorae is an engaging study group due to its early diversification compared to most Carex lineages, and its remarkable disjunct distribution in four continents corresponding to three independent sections: sect. Psyllophorae in Western Palearctic, sect. Schoenoxiphium in Afrotropical region, and sect. Junciformes in South America (SA) and SW Pacific. The latter section is mainly distributed in Patagonia and the Andes, where it is one of the few Carex groups with a significant in situ diversification. We assess the role of historical geo-climatic events in the evolutionary history of the group, particularly intercontinental colonization events and diversification processes, with an emphasis on SA. We performed an integrative study using phylogenetic (four DNA regions), divergence times, diversification rates, biogeographic reconstruction, and bioclimatic niche evolution analyses. The crown age of subg. Psyllophorae (early Miocene) supports this lineage as one of the oldest within Carex. The diversification rate probably decreased over time in the whole subgenus. Geography seems to have played a primary role in the diversification of subg. Psyllophorae. Inferred divergence times imply a diversification scenario away from primary Gondwanan vicariance hypotheses and suggest long-distance dispersal-mediated allopatric diversification. Section Junciformes remained in Northern Patagonia since its divergence until Plio-Pleistocene glaciations. Andean orogeny appears to have acted as a northward corridor, which contrasts with the general pattern of North-to-South migration for temperate-adapted organisms. A striking niche conservatism characterizes the evolution of this section. Colonization of the SW Pacific took place on a single long-distance dispersal event from SA. The little ecological changes involved in the trans-Pacific disjunction imply the preadaptation of the group prior to the colonization of the SW Pacific. The high species number of the section results from simple accumulation of morphological changes (disparification), rather than shifts in ecological niche related to increased diversification rates (radiation).

New relevant chorological and conservation data on Carex (Cyperaceae) and Hypericum (Hypericaceae) from Ecuador

“…Peterm. ), one of the few Carex groups with a remarkably relatively high species diversity in South America ( Benítez-Benítez et al 2021a ). Carex phalaroides is an anomalous member of sect.…”

“… Carex phalaroides is an anomalous member of sect. Junciformes from a morphological point of view as its inflorescence is constituted by several spikes (instead of a solitary one in the remainder of the section) ( Benítez-Benítez et al 2021a , Morales-Alonso et al, in prep.).…”

“… Junciformes (subg. Psyllophorae ), a group with its centres of origin and diversity in Patagonia ( Benítez-Benítez et al 2021a ).…”

Geometric Morphometrics sheds light on the systematics affinities of two enigmatic dwarf Neotropical sedges (Carex, Cyperaceae)

“…The C. phalaroides gr. species are ecologically atypical among Neotropical sedges as they primarily occur in temperate and subtropical habitats, such as the Atlantic forest and pampas ( Benítez-Benítez et al 2021 ). Despite their initial attribution to the C. phalaroides gr., both C. herteri and C. hypsipedos display characters that would be deviant within it.…”

The genus Carex (Cyperaceae) in Chile: a general update of its knowledge, with an identification key

“…However, this work has been mostly neglected because it is written in French and is hard to find. So usually, for sedge identification, Chilean botanists and amateurs must resort to Flora Patagonica (Barros 1969) or other Argentinian floras (e.g., Genera et Species Plantarum Argentinarum (Barros 1943); Flora de la Provincia de Buenos Aires (Pedersen 1969); Flora de San Juan (Wheeler 2009)). However, these works are not directly related to Chile or leave uncovered a large area of it, thus many Chilean species may be not present in these.…”