Time-calibrated phylogenies reveal mediterranean and pre-mediterranean origin of the thermophilous vegetation of the Canary Islands

Abstract

Background and Aims The Canary Islands have strong floristic affinities with the Mediterranean Basin. One of the most characteristic and diverse vegetation belt of the archipelago is the thermophilous woodland (between 200 and 900 m.a.s.l.). This thermophilous plant community consists of many non-endemic species shared with the Mediterranean Floristic Region together with Canarian endemic species. Consequently, phytogeographic studies have historically proposed the hypothesis of an origin of the Canarian thermophilous species following the establishment of the summer-dry mediterranean climate in the Mediterranean Basin around 2.8 million years ago. Methods Time-calibrated phylogenies for 39 plant groups including Canarian thermophilous species were primarily analysed to infer colonization times. In particular, we used 26 previously-published phylogenies together with 13 time-calibrated phylogenies (including newly generated plastid and nuclear DNA sequence data) to assess whether the time interval between stem and crown ages of Canarian thermophilous lineages postdates 2.8 Ma. For lineages postdating this time threshold, we additionally conducted ancestral area reconstructions to infer the potential source area for colonization. Key Results A total of 43 Canarian thermophilous lineages were identified from 39 plant groups. Both mediterranean (16) and pre-mediterranean (9) plant lineages were found. However, we failed to determine the temporal origin for 18 lineages because a stem-crown time interval overlaps with the 2.8 Ma threshold. The spatial origin of thermophilous lineages was also heterogeneous, including ancestral areas from the Mediterranean Basin (nine) and other regions (six). Conclusions Our findings reveal an unexpectedly heterogeneous origin of the Canarian thermophilous species in terms of colonization times and mainland source areas. A substantial proportion of the lineages arrived in the Canaries before the summer-dry climate was established on the Mediterranean Basin. The complex temporal and geographical origin of Canarian thermophilous species challenges the view of the Canary Islands (and Madeira) as a subregion within the Mediterranean Floristic Region.

Repeated asynchronous evolution of single‐species endemics of ivies (Hedera L.) in Macaronesian archipelagos

“…We used phylogenomic and climatic niche analyses to disentangle the spatio-temporal origin and evolutionary patterns of three singlespecies endemics of the same genus (Hedera, ivies) from different, Macaronesian archipelagos by ivies, and occurred between the late Pliocene and the Pleistocene (1.37-4.57 Ma considering crown and stem ages, see Martín-Hernanz et al, 2023 for a discussion on the relevance of considering both ages; Figure 4). This recent colonization explains the pattern of budding speciation detected (see also Alonso et al, 2022; Figure 2).…”

Phylogenetics and phylogeography ofEuphorbia canariensisreveal an extreme Canarian-Asian disjunction and limited inter-island colonization

“…This fact, together with the apparently low colonization capabilities of E. canariensis (considering the lack of LDD syndromes and the relatively low estimated number of inter-island colonization events despite a relatively old age), supports the idea of extinction of intermediate relatives of E. canariensis in Africa and southwestern Asia. This extreme Canarian-Asian disjunction deserves exploration in other plant groups, such as Apollonias and Bosea (Li et al, 2011;Martín-Hernanz et al, 2023). Tables Table 1: Primers used for amplification and sequencing of two cpDNA regions (trnS-trnG and trnQ-rps16) and the nDNA (ITS) in Euphorbia species.…”

“…The relatively recent divergence among E. canariensis haplotypes in the Canary Islands (crown age, 1.76 -2.27 Ma; Figure 5) contrasts with the old divergence between this species and its close relatives (stem age, 3.95 -12.68 Ma; Figure 2). This implies a high uncertainty on the time of colonization of the Canary Islands from the continent, which may have happened at any point between the stem age and the crown age (Martín-Hernanz et al, 2023). Indeed, the geographic and genetic distance between E. canariensis and its closest relatives highlights the problem of incomplete taxon sampling (due to extinction or unsampled close relatives).…”

Phylogenetics and phylogeography of Euphorbia canariensis reveal an extreme Canarian‐Asian disjunction but limited inter‐island colonization

“…2A). This implies a high uncertainty on the time of colonization of the Canary Islands from the continent, which may have happened at any point between the stem age and the crown age (Mart ın-Hernanz et al 2023). It is possible that the colonization of the Canarian archipelago from the continent occurred long before the estimated crown age if the E. canariensis lineage experienced significant extinction in the Canary Islands in the past (Garc ıa-Verdugo et al 2019b).…”