Date Published: February 13, 2019
Publisher: Public Library of Science
Author(s): Beatriz Vigalondo, Jairo Patiño, Isabel Draper, Vicente Mazimpaka, James R. Shevock, Ana Losada-Lima, Juana M. González-Mancebo, Ricardo Garilleti, Francisco Lara, Berthold Heinze.
Biogeography, systematics and taxonomy are complementary scientific disciplines. To understand a species’ origin, migration routes, distribution and evolutionary history, it is first necessary to establish its taxonomic boundaries. Here, we use an integrative approach that takes advantage of complementary disciplines to resolve an intriguing scientific question. Populations of an unknown moss found in the Canary Islands (Tenerife Island) resembled two different Californian endemic species: Orthotrichum shevockii and O. kellmanii. To determine whether this moss belongs to either of these species and, if so, to explain its presence on this distant oceanic island, we combined the evaluation of morphological qualitative characters, statistical morphometric analyses of quantitative traits, and molecular phylogenetic inferences. Our results suggest that the two Californian mosses are conspecific, and that the Canarian populations belong to this putative species, with only one taxon thus involved. Orthotrichum shevockii (the priority name) is therefore recognized as a morphologically variable species that exhibits a transcontinental disjunction between western North America and the Canary Islands. Within its distribution range, the area of occupancy is limited, a notable feature among bryophytes at the intraspecific level. To explain this disjunction, divergence time and ancestral area estimation analyses are carried out and further support the hypothesis of a long-distance dispersal event from California to Tenerife Island.
Since Wegener’s plate tectonics theory was proposed, ancient fragmentation has long been considered the main process explaining common distribution patterns in plant biogeography , while dispersal is seen as a random and irrelevant process . However, more recent molecular tools and the development of dating and divergence time estimations have pointed to dispersal as a key process contributing to current species distributions [3–7]. In the case of oceanic islands, which originate without a former connection to a continental landmass, dispersal is considered to play a fundamental role in the generation of biodiversity and biogeographical patterns [2,8–12]. For the Macaronesian islands, a biogeographic region that encompasses the archipelagos of the Canary Islands, the Azores, Madeira and Cabo Verde (but see Vanderpoorten et al. 2007), it has been suggested that the endemic bryophyte component of the flora has a different biogeographical origin compared to angiosperms. This pattern has been explained, at least partially, by their different dispersal capabilities, since ancestors of a few endemic bryophytes seem to have colonized the islands from more distant continental pools [13,14]. Similarly, compared to tracheophytes, the larger distribution ranges of bryophytes have been attributed to their higher dispersal capabilities . In many cases, these ranges involve intercontinental disjunctions at the species level, while in vascular plants these mostly occur at a genus level [15,16].
Field collecting permits were granted by both California state and federal ownership, where applicable, as well as from Parque Nacional del Teide.