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

Abstract

AimEvolutionary studies of oceanic island endemics are usually focused on lineages that have experienced in situ radiation, while those that speciated once on the island or archipelago but have not further diversified (single‐species endemics) remain understudied. The Macaronesian archipelagos, in the Atlantic Ocean, are home to significant numbers of single‐species endemics. The genus Hedera L. (12 species) includes three single‐species endemics from three Macaronesian archipelagos with putatively independent origins. Here, we tested the role of phylogenetic niche conservatism in their evolution. To that end, we (1) reconstructed the spatio‐temporal origin of Macaronesian ivies using phylogenomics, and (2) assessed the role of climatic niche during their colonization and speciation.LocationAzores, Canary Islands, Madeira, western Mediterranean.TaxonHedera spp.MethodsWe used 166 samples representing all Hedera species to generate genotyping‐by‐sequencing (GBS) libraries and performed time‐calibrated phylogenomic and biogeographic analyses. Climatic preferences and climatic niche evolution were assessed using a geo‐referenced database of the western ivy species (2,297 records).ResultsIndependent and asynchronous colonization and speciation were estimated for the three Macaronesian ivies, resulting in different degrees of phylogenetic and climatic niche differentiation: H. canariensis displayed an early divergence (7.5–12 Ma) and high phylogenetic and niche isolation; H. azorica had intermediate phylogenetic isolation and niche divergence from its closest relative H. helix (4.4–6.8 Ma) and H. maderensis was embedded within the climatically similar H. iberica (2.8–4.6 Ma). A strong phylogenetic signal was suggested for climatic niche in the western clade of Hedera, where the three Macaronesian ivies are placed.Main ConclusionsThe three Macaronesian ivies represent the evolutionary stages leading to the emergence of single‐species island endemics. Climatic niche conservatism appears to be involved in the evolution of single‐species endemics, first by facilitating island colonization, and then by limiting in situ diversification.

Extensive misidentification of European ivy species (Hedera L.): How taxonomically reliable are online biodiversity databases?

“…4) is unlikely because the climate in these areas is not as warm and humid as the preferred by H. canariensis 19 . The case of H. maroccana is different as the climate that this species occupies in its native range in Morocco is also present in part of the areas in mainland Europe where it has been recorded 19 (Fig. 4).…”

“…The six study ivy species generally grow in shady, moist places such as riverbanks, ravines or forest understories, with a different degree of tolerance to dry, sunny places such as exposed rock faces 19,29 . Indeed, some species, such as the common ivy (H. helix L.), can survive over a wide range of temperatures and rainfall regimes 29 .…”

“…Additionally, we analyzed 479 individuals from 117 populations of the four native ivy species collected in the Iberian Peninsula and Madeira (identi ed in the database as "NiDEvA project"). These individuals were originally collected by the authors of this study during the eldwork of a scienti c project (NiDEvA project), the specimens were deposited at MAUAM and were partially used in two molecular studies 19,29 . Species identi cation followed Valcárcel and Vargas taxonomic criterion 21 and was mainly based on micromorphological information from foliar trichomes and macromorphological characters, mostly from vegetative leaves.…”

High rate of species misidentification reduces the taxonomic certainty of European biodiversity databases of ivies (Hedera L.)

“…The species studied generally grow in shady, moist places such as riverbanks, ravines or forest understories, with varying degrees of tolerance to dry, sunny locations such as exposed rock faces 20 , 27 . Indeed, some species, such as the common ivy ( H. helix L.), can survive over a wide range of temperatures and rainfall regimes 27 .…”

“…This is the case for ivies ( Hedera L.), a small genus with recent diversification 20 and extensive hybridization 21 , where species delimitation has long been controversial 22 and species identification difficult 23 . Identification of ivy species is based on inconspicuous microscopic characters (trichomes) that are difficult to interpret while macroscopic characters (leaves, flowers or fruits) tend to be of little taxonomic importance 22 .…”