Genome size variation within Crithmum maritimum: Clues on the colonization of insular environments.

Angiosperms present an astonishing diversity of genome sizes that can vary intra- or interspecifically. The remarkable new cytogenomic data shed some light on our understanding of evolution, but few studies were performed with insular and mainland populations to test possible correlations with dispersal, speciation, and adaptations to insular environments. Here, patterns of cytogenomic diversity were assessed among geographic samples (ca. 114) of Crithmum maritimum (Apiaceae), collected across the Azores and Madeira archipelagos, as well as in adjacent continental areas of Portugal. Using flow cytometry, the results indicated a significant intraspecific genome size variation, spanning from reduced sizes in the insular populations to larger ones in the mainland populations. Moreover, there was a tendency for an increase in genome size along the mainland populations, associated with lower temperatures, higher precipitation, and lower precipitation seasonality. However, this gradient might be the result of historic phylogeographical events associated with previous dispersal and extinction of local populations. Overall, our findings provided evidence that smaller genome sizes might play a critical role in the colonization of islands, corroborating other studies that argue that organisms with smaller genomes use fewer resources, having a selective advantage under insular environments. Although further studies are needed to improve our understanding of the mechanisms underlying genome size evolution on islands, conservation strategies must be promoted to protect the rich cytogenomic diversity found among C. maritimum populations, which occur in coastal areas that are particularly threatened by human activity, pollution, invasive species, and climate changes.

Multiplexed shotgun genotyping (MSG) data resolve phylogenetic relationships within and among archipelagos in Macaronesian Tolpis.

PREMISE: Plants endemic to oceanic archipelagos are suitable for studying evolution, being isolated on substrates of different ages. Evolution has been recent, rendering traditionally employed sequences insufficiently variable for resolving relationships. This study includes sampling in the genus Tolpis (Asteraceae) from the Azores, Madeira, and Cape Verde, and expands upon an earlier study demonstrating the efficacy of multiplexed shotgun genotyping (MSG) for resolving relationships in Canarian Tolpis. METHODS: Genomic libraries for 90 accessions of Tolpis and two from the outgroup were generated for genotyping individuals using MSG. Loci were de novo assembled with iPyrad, which clusters MSG loci within and between samples. A maximum likelihood phylogeny was generated with RAxML. Ancestral area reconstruction was inferred using R package BioGeoBEARS. RESULTS: MSG data recovered a highly resolved phylogeny from population to inter-archipelago levels. Ancestral area reconstruction provided biogeographic hypotheses for the radiation of Macaronesian Tolpis. CONCLUSIONS: Four major clades were resolved. The Madeiran endemic T. macrorhiza is sister to other Tolpis. Species from the Canaries, Cape Verdes, and the continent are sister to T. succulenta from Madeira, which has a sister subclade of Azorean populations composed of T. succulenta and T. azorica. Population-level resolution suggests unrecognized taxa on several archipelagos. Ancestral reconstruction suggests initial dispersal from the continent to Madeira, with dispersal to the Azores, then dispersal from Madeira to the Canary Islands, with both subsequent dispersal to the Cape Verdes and back-dispersal to the continent. Single-island radiations and inter-island dispersal are implicated in divergence in Macaronesian Tolpis.

Diversity and Cytogenomic Characterization of Wild Carrots in the Macaronesian Islands.

The Macaronesian islands constitute an enormous reservoir of genetic variation of wild carrots (subtribe Daucinae; Apiaceae), including 10 endemic species, but an accurate understanding of the diversification processes within these islands is still lacking. We conducted a review of the morphology, ecology, and conservation status of the Daucinae species and, on the basis of a comprehensive dataset, we estimated the genome size variation for 16 taxa (around 320 samples) occurring in different habitats across the Macaronesian islands in comparison to mainland specimens. Results showed that taxa with larger genomes (e.g., Daucus crinitus: 2.544 pg) were generally found in mainland regions, while the insular endemic taxa from Azores and Cabo Verde have smaller genomes. Melanoselinum decipiens and Monizia edulis, both endemic to Madeira Island, showed intermediate values. Positive correlations were found between mean genome size and some morphological traits (e.g., spiny or winged fruits) and also with habit (herbaceous or woody). Despite the great morphological variation found within the Cabo Verde endemic species, the 2C-values obtained were quite homogeneous between these taxa and the subspecies of Daucus carota, supporting the close relationship among these taxa. Overall, this study improved the global knowledge of DNA content for Macaronesian endemics and shed light into the mechanisms underpinning diversity patterns of wild carrots in the western Mediterranean region.

Genome-wide genotyping estimates mating system parameters and paternity in the island species Tolpis succulenta.

PREMISE: The mating system has profound consequences, not only for ecology and evolution, but also for the conservation of threatened or endangered species. Unfortunately, small populations are difficult to study owing to limits on sample size and genetic marker diversity. Here, we estimated mating system parameters in three small populations of an island plant using genomic genotyping. Although self-incompatible (SI) species are known to often set some self-seed, little is known about how "leaky SI" affects selfing rates in nature or the role that multiple paternity plays in small populations. METHODS: We generalized the BORICE mating system program to determine the siring pattern within maternal families. We applied this algorithm to maternal families from three populations of Tolpis succulenta from Madeira Island and genotyped the progeny using RADseq. We applied BORICE to estimate each individual offspring as outcrossed or selfed, the paternity of each outcrossed offspring, and the level of inbreeding of each maternal plant. RESULTS: Despite a functional self-incompatibility system, these data establish T. succulenta as a pseudo-self-compatible (PSC) species. Two of 75 offspring were strongly indicated as products of self-fertilization. Despite selfing, all adult maternal plants were fully outbred. There was high differentiation among and low variation within populations, consistent with a history of genetic isolation of these small populations. There were generally multiple sires per maternal family. Twenty-two percent of sib contrasts (between outcrossed offspring within maternal families) shared the same sire. CONCLUSIONS: Genome-wide genotyping, combined with appropriate analytical methods, enables estimation of mating system and multiple paternity in small populations. These data address questions about the evolution of reproductive traits and the conservation of threatened populations.

The first Ichneumonid fossil from the Early Pleistocene of Madeira Island (Portugal).

In oceanic islands, well age-constrained deposits containing arthropod somatofossils (body fossils) are rare. However, when available, these are important for providing empirical and independent minimum ages for molecular phylogenetic dating and complementary data on taxonomy, evolution and palaeobiogeography information of the biological groups found as fossils. This is especially important for taxa that speciated within oceanic islands, many becoming single island endemics (SIE). Recently, associated with a 1.3 Ma (Calabrian) fluvial and lacustrine sedimentary deposit from Porto da Cruz in Madeira Island (Fig. 1), a wing, putatively identified as Hymenoptera, was found. Here we describe this wing fossil as belonging to Ichneumonidae, a group with ca. 30% of SIE in Madeira Island. Moreover, this is the first somatofossil of ichneumonid parasitic wasps found in Madeira Island and in Macaronesian islands (i.e. Azores, Madeira, Canaries and Cabo Verde).

Are there any widespread endemic flowering plant species in Macaronesia? Phylogeography of Ranunculus cortusifolius.

PREMISE OF THE STUDY: Oceanic island endemics typically exhibit very restricted distributions. In Macaronesia, only one endemic angiosperm species, Ranunculus cortusifolius, has a distribution spanning the archipelagos of the Azores, Madeira, and Canaries. Earlier work suggested possible differences between archipelagos and the multiple origins of the species. This paper tests the hypothesis that R. cortusifolius is a single widespread Macaronesian endemic species with a single origin. METHODS: Chloroplast (matK-trnK, psbJ-petA) and ITS sequences were generated from across the distribution of R. cortusifolius. Relationships were investigated using Bayesian inference and divergence times estimated using BEAST. Infraspecific variation was investigated using statistical parsimony. The general mixed Yule-coalescent model (GMYC) was further used to identify putative species boundaries based on maternally inherited plastid data. KEY RESULTS: The hypothesis of multiple independent origins of R. cortusifolius is rejected. Divergence of the R. cortusifolius lineage from a western Mediterranean sister group in the late Miocene is inferred. Distinct genotypes were resolved within R. cortusifolius that are endemic to the Azores, Madeira, and the Canaries. Four to five putative species were delimited by different versions of the GMYC model. CONCLUSION: Ranunculus cortusifolius is the result of a single colonization of Macaronesia. The large distances between archipelagos have been effective barriers to dispersal, promoting allopatric diversification at the molecular level with diversification also evident within the Canaries. Isolation has not been accompanied by marked morphological diversification, which may be explained by the typical association of R. cortusifolius with stable and climatically buffered laurel forest communities.

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.