Canary Islands (NE Atlantic) as a biodiversity "hotspot" of Gambierdiscus: Implications for future trends of ciguatera in the area

In the present study the geographical distribution, abundance and composition of Gambierdiscus was described over a 600 km longitudinal scale in the Canary Islands. Samples for cell counts, isolation and identification of Gambierdiscus were obtained from five islands (El Hierro, Tenerife, Gran Canaria, Fuerteventura and Lanzarote). Average densities of Gambierdiscus spp. between 0 and 2200 cells g−1 blot dry weight of macrophyte were recorded. Morphological (light microscopy and SEM techniques) and molecular analyses (LSU and SSU rDNA sequencing of cultures and single cells from the field) of Gambierdiscus was performed. Five Gambierdiscus species (G. australes, G. caribaeus, G. carolinianus, G. excentricus and G. silvae), together with a new putative species (Gambierdiscus ribotype 3) were identified. These results suggest that some cases of CFP in the region could be associated with the accumulation of ciguatoxins in the marine food web acquired from local populations of Gambierdiscus. This unexpected high diversity of Gambierdiscus species in an area which a priori is not under risk of ciguatera, hints at an ancient settlement of Gambierdiscus populations, likely favored by warmer climate conditions in the Miocene Epoch (when oldest current Canary Islands were created), in contrast with cooler present ones. Currently, warming trends associated with climate change could contribute to extend favorable environmental conditions in the area for Gambierdiscus growth especially during winter months.Postprin

Colonization and diversification shape species–area relationships in three Macaronesian archipelagos

Aim: Species–area relationships (SARs) on oceanic archipelagos are shaped at least as much by speciation as by immigration–extinction dynamics. We examine three well‐studied Atlantic archipelagos to quantify the relative contributions of colonization and diversification to individual and whole‐archipelago floras. Location: Three Macaronesian archipelagos: the Azores, Madeira and Canary Islands. Methods: We assessed the floras of all three archipelagos in order to compare SARs and numbers of endemic species with respect to the physical characteristics of each archipelago (geological age, isolation, and environmental diversity). Utilizing a large number of available phylogenies, we partitioned each flora into putative colonist lineages. These were used to determine: (a) the number of original colonists of each archipelago, (b) degree of relatedness among these, and (c) the degree to which internal diversification contributes to species numbers for islands and archipelagos with different physical characteristics. Results: Archipelagos varied in the parameters of the SARs in relation to their physical characteristics. The Canarian and Madeiran floras demonstrate remarkably similar SARs with z values (slopes) near 0.3, while the Azorean flora exhibits fewer species per given area and a modest z value of 0.15. The Canarian and Madeiran endemic species are concentrated in a small number of diversifying lineages, whereas the Azorean endemics were mostly in anagenetic lineages (indicating minimal internal diversification). Lineages that do not diversify within a given archipelago significantly tend not to diversify in others, whereas diversifying lineages tend to have more species in the Canarian flora when compared with related lineages in the others. Main conclusions: Although a strong independent effect of island area on species richness exists for the whole Macaronesian region, colonization and diversification are also influenced by geological age and environmental diversity of archipelagos, overriding characteristics of individual islands (“archipelago effect”). The “Azorean diversity enigma” likely results from a combination of geological youth, low environmental diversity and disproportionate human alteration

Biogeography of Mediterranean hotspot biodiversity: re-evaluating the 'Tertiary relict' hypothesis of Macaronesian laurel forests

The Macaronesian laurel forests (MLF) are dominated by trees with a laurophyll habit comparable to evergreen humid forests which were scattered across Europe and the Mediterranean in the Paleogene and Neogene. Therefore, MLF are traditionally regarded as an old, 'Tertiary relict' vegetation type. Here we address the question if key taxa of the MLF are relictual. We evaluated the relict hypothesis consulting fossil data and analyses based on molecular phylogenies of 18 representative species. For molecular dating we used the program BEAST, for ancestral trait reconstructions BayesTraits and Lagrange to infer ancestral areas. Our molecular dating showed that the origins of four species date back to the Upper Miocene while 14 originated in the Plio-Pleistocene. This coincides with the decline of fossil laurophyllous elements in Europe since the middle Miocene. Ancestral trait and area reconstructions indicate that MLF evolved partly from pre-adapted taxa from the Mediterranean, Macaronesia and the tropics. According to the fossil record laurophyllous taxa existed in Macaronesia since the Plio- and Pleistocene. MLF are composed of species with a heterogeneous origin. The taxa dated to the Pleistocene are likely not 'Tertiary relicts'. Some species may be interpreted as relictual. In this case, the establishment of most species in the Plio-Pleistocene suggests that there was a massive species turnover before this time. Alternatively, MLF were largely newly assembled through global recruitment rather than surviving as relicts of a once more widespread vegetation. This process may have possibly been triggered by the intensification of the trade winds at the end of the Pliocene as indicated by proxy data

Results of BayesTraits analyses concerning laurel forest ecology (columns 2–3) and morphological traits (columns 4–11).

<p>MRCA: most recent common ancestor; P: Posterior probability; LF: laurel forest; Ev: evergreen; H: herbaceous; W: woody habit; Pn: perennial; A: annual; En: entire leave margin. P value > 0.6 in bold letters., < 0.4 in italics.</p><p>Results of BayesTraits analyses concerning laurel forest ecology (columns 2–3) and morphological traits (columns 4–11).</p

Optimisation of morphological traits to the mrca of the MLF species/sister in a radar plot.

<p>In the outer circle laurophyllous traits are supported by BayesTraits analyses, in the inner circle they are rejected, in the middle circle the optimisation is ambiguous. The cutting value for the marginal probability: > 0.6, accepted; 0.6–0.5, ambiguous; < 0.4, rejected.</p

Stem age estimates of the studied laurel forest species (Ma: million years ago).

<p>Bars show the 95% HPD, mean stem ages are marked by a vertical black line. Asterisks (*) indicate taxa whose mrca habitat is not optimised as laurel forest.</p

Stem age estimates of MLF taxa using BEAST as means and 95% highest posterior densities (HPD) in Ma.

<p>Stem age estimates of MLF taxa using BEAST as means and 95% highest posterior densities (HPD) in Ma.</p

Source areas of Macaronesian laurel forest taxa as indicated by Lagrange.

<p>A) Proportion of area or area combinations as ancestral area for MLF based on relative probabilities over all taxa. B) Area reconstruction of each taxon with a likelihood > 10%. X-axis represents relative probabilities. Colours: (lilac) Macaronesia (Azores, Madeira, Canary Islands), (light blue) Europe incl. Mediterranean, (yellow) Asia, (dark red) North and South America, (green) Africa.</p