Patterns and drivers of species diversity in the Indo‐Pacific red seaweed Portieria

Abstract

Aim Biogeographical processes underlying Indo‐Pacific biodiversity patterns have been relatively well studied in marine shallow water invertebrates and fishes, but have been explored much less extensively in seaweeds, despite these organisms often displaying markedly different patterns. Using the marine red alga Portieria as a model, we aim to gain understanding of the evolutionary processes generating seaweed biogeographical patterns. Our results will be evaluated and compared with known patterns and processes in animals. Location Indo‐Pacific marine region. Methods Species diversity estimates were inferred using DNA‐based species delimitation methods. Historical biogeographical patterns were inferred based on a six‐gene time‐calibrated phylogeny, distribution data of 802 specimens, and probabilistic modelling of geographical range evolution. The importance of geographical isolation for speciation was further evaluated by population genetic analyses at the intraspecific level. Results We delimited 92 candidate species, most with restricted distributions, suggesting low dispersal capacity. Highest species diversity was found in the Indo‐Malay Archipelago (IMA). Our phylogeny indicates that Portieria originated during the late Cretaceous in the area that is now the Central Indo‐Pacific. The biogeographical history of Portieria includes repeated dispersal events to peripheral regions, followed by long‐term persistence and diversification of lineages within those regions, and limited dispersal back to the IMA. Main conclusions Our results suggest that the long geological history of the IMA played an important role in shaping Portieria diversity. High species richness in the IMA resulted from a combination of speciation at small spatial scales, possibly as a result of increased regional habitat diversity from the Eocene onwards, and species accumulation via dispersal and/or island integration through tectonic movement. Our results are consistent with the biodiversity feedback model, in which biodiversity hotspots act as both “centres of origin” and “centres of accumulation,” and corroborate previous findings for invertebrates and fish that there is no single unifying model explaining the biological diversity within the IMA.

Phylogeography of the Hypnea musciformis species complex (Gigartinales, Rhodophyta) with the recognition of cryptic species in the western Atlantic Ocean

“…Instead of one or two widespread species, our results suggest the possibility of the existence several cryptic species that have more restricted patterns of distribution similar to what has been reported for other hitherto widely distributed red macroalgal taxa, such as Portieria hornemanii (Leliaert et al. ) and Lobophora variegata (Vieira et al. ).…”

“…Hypnea musciformis from the Mexican Pacific coast might represent a fifth species. Instead of one or two widespread species, our results suggest the possibility of the existence several cryptic species that have more restricted patterns of distribution similar to what has been reported for other hitherto widely distributed red macroalgal taxa, such as Portieria hornemanii (Leliaert et al 2018) and Lobophora variegata (Vieira et al 2017). Furthermore, our results indicate the source of possible recent introductions for species of the complex, as in the case of Hawaii and, possibly, Ghana and Namibia in Africa.…”

Dissecting biodiversity in a global hotspot: Uneven dynamics of immigration and diversification within the Cape Floristic Region of South Africa

“…Furthermore, the fact that this region is the one with the highest relative contribution of speciation also supports theoretical arguments for a role of increasing age, area and heterogeneity in driving in situ speciation within a region (Losos & Schluter, ). Such a pattern of a diversity centre with dispersal outwards, while retaining a high local diversification, was also demonstrated for the Southern Hemisphere with Australia as a source (Crisp et al, ), for the Neotropics occupied from Amazonia (Antonelli et al, ), and for red algae in the Indo‐Pacific, expanding outwards from the Indo‐Malay Archipelago (Leliaert et al, ) and may be quite common. The implication is that the Southwestern Mountain region acted as central cradle for diversity that over time built up the exceptional CFR diversity, both by in situ speciation and by seeding lineages into neighbouring regions, as well as further afield to the whole African montane flora (Linder & Verboom, ).…”

Historical biogeography of the widespread macroalga Sargassum (Fucales, Phaeophyceae)

“…) and red macroalga Portieria (Gigartinales, Rhizophyllidaceae; Leliaert et al. ). Likewise, the cosmopolitan genus Sargassum , which comprises over 350 currently accepted species (Guiry and Guiry ), exhibits a similar pattern by dominating the tropical and subtropical regions (Mattio and Payri ).…”