Climate drives community-wide divergence within species over a limited spatial scale: evidence from an oceanic island.

Geographic isolation substantially contributes to species endemism on oceanic islands when speciation involves the colonisation of a new island. However, less is understood about the drivers of speciation within islands. What is lacking is a general understanding of the geographic scale of gene flow limitation within islands, and thus the spatial scale and drivers of geographical speciation within insular contexts. Using a community of beetle species, we show that when dispersal ability and climate tolerance are restricted, microclimatic variation over distances of only a few kilometres can maintain strong geographic isolation extending back several millions of years. Further to this, we demonstrate congruent diversification with gene flow across species, mediated by Quaternary climate oscillations that have facilitated a dynamic of isolation and secondary contact. The unprecedented scale of parallel species responses to a common environmental driver for evolutionary change has profound consequences for understanding past and future species responses to climate variation.

Core and symbiotic genes reveal nine Mesorhizobium genospecies and three symbiotic lineages among the rhizobia nodulating Cicer canariense in its natural habitat (La Palma, Canary Islands).

Cicer canariense is a threatened perennial wild chickpea endemic to the Canary Islands. In this study, rhizobia that nodulate this species in its natural habitats on La Palma (Canary Islands) were characterised. The genetic diversity and phylogeny were estimated by RAPD profiles, 16S-RFLP analysis and sequencing of the rrs, recA, glnII and nodC genes. 16S-RFLP grouped the isolates within the Mesorhizobium genus and distinguished nine different ribotypes. Four branches included minority ribotypes (3-5 isolates), whereas another five contained the predominant ribotypes that clustered with reference strains of M. tianshanense/M. gobiense/M. metallidurans, M. caraganae, M. opportunistum, M. ciceri and M. tamadayense. The sequences confirmed the RFLP groupings but resolved additional internal divergence within the M. caraganae group and outlined several potential novel species. The RAPD profiles showed a high diversity at the infraspecific level, except in the M. ciceri group. The nodC phylogeny resolved three symbiotic lineages. A small group of isolates had sequences identical to those of symbiovar ciceri and were only detected in M. ciceri isolates. Another group of sequences represented a novel symbiotic lineage that was associated with two particular chromosomal backgrounds. However, nodC sequences closely related to symbiovar loti predominated in most isolates, and they were detected in several chromosomal backgrounds corresponding to up to nine Mesorhizobium lineages. The results indicated that C. canariense is a promiscuous legume that can be nodulated by several rhizobial species and symbiotypes, which means it will be important to determine the combination of core and symbiotic genes that produce the most effective symbiosis.

Bioclimatic and vegetation mapping of a topographically complex oceanic island applying different interpolation techniques.

Different spatial interpolation techniques have been applied to construct objective bioclimatic maps of La Palma, Canary Islands. Interpolation of climatic data on this topographically complex island with strong elevation and climatic gradients represents a challenge. Furthermore, meteorological stations are not evenly distributed over the island, with few stations at high elevations. We carried out spatial interpolations of the compensated thermicity index (Itc) and the annual ombrothermic Index (Io), in order to obtain appropriate bioclimatic maps by using automatic interpolation procedures, and to establish their relation to potential vegetation units for constructing a climatophilous potential natural vegetation map (CPNV). For this purpose, we used five interpolation techniques implemented in a GIS: inverse distance weighting (IDW), ordinary kriging (OK), ordinary cokriging (OCK), multiple linear regression (MLR) and MLR followed by ordinary kriging of the regression residuals. Two topographic variables (elevation and aspect), derived from a high-resolution digital elevation model (DEM), were included in OCK and MLR. The accuracy of the interpolation techniques was examined by the results of the error statistics of test data derived from comparison of the predicted and measured values. Best results for both bioclimatic indices were obtained with the MLR method with interpolation of the residuals showing the highest R2 of the regression between observed and predicted values and lowest values of root mean square errors. MLR with correction of interpolated residuals is an attractive interpolation method for bioclimatic mapping on this oceanic island since it permits one to fully account for easily available geographic information but also takes into account local variation of climatic data.

Lotus endemic to the Canary Islands are nodulated by diverse and novel rhizobial species and symbiotypes.

Genetic and symbiotic characterization of 34 isolates from several Lotus species endemic to the Canary Islands showed extraordinary diversity, with bacteria belonging to different species of the genera Mesorhizobium (17 isolates), Sinorhizobium (12 isolates) and Rhizobium/Agrobacterium (5 isolates). In a previous report, we showed that the Sinorhizobium isolates mostly belonged to S. meliloti. Here, we focused on the remaining isolates. The Lotus mesorhizobial strains were distributed in the rrs tree within six poorly resolved branches. Partial sequences from atpD and recA genes produced much better resolved phylogenies that were, with some exceptions, congruent with the ribosomal phylogeny. Thus, up to six different mesorhizobial species were detected, which matched with or were sister species of M. ciceri, M. alhagi, M. plurifarium or M. caraganae, and two represented new lineages that did not correspond to any of the currently recognized species. Neither M. loti nor Bradyrhizobium sp. (Lotus), recognized as the typical Lotus-symbionts, were identified among the Canarian Lotus isolates, although their nodulation genes were closely related to M. loti. However, several subbranches of mesorhizobia nodulating Lotus spp. could be differentiated in a nodC tree, with the isolates from the islands distributed in two of them (A1 and A3). Subbranch A1 included reference strains of M. loti and a group of isolates with a host range compatible with biovar loti, whereas A3 represented a more divergent exclusive subbranch of isolates with a host range almost restricted to endemic Lotus and it could represent a new biovar among the Lotus rhizobia.

Pancratium canariense as an important source of amaryllidaceae alkaloids.

Four new alkaloids (1-4) have been isolated from a methanolic extract of bulbs of Pancratium canariense, together with 12 known alkaloids (5-16). The structures of the new alkaloids were determined by extensive 1D and 2D NMR spectroscopic studies and X-ray diffraction.

Different Mesorhizobium species sharing the same symbiotic genes nodulate the shrub legume Anagyris latifolia.

The isolation and characterization of six rhizobial strains isolated from Anagyris latifolia, a shrub legume endemic to the Canary Islands, is reported in this study. The isolates were characterized by 16S-ARDRA, and sequencing of the ribosomal 16SrRNA gene, the 16S-23SrDNA intergenic spacer region, and the housekeeping gene for glutamine synthetase II (glnII). The phylogenies based on the three types of sequences matched, showing that the isolates belonged to three distinct lineages within the genus Mesorhizobium that could represent different species. However, the ribosomal and glnII phylogenies revealed some discrepancies in the relationships between the isolates and the named species in this genus. Despite their different taxonomic affiliation, all the isolates showed identical nodC sequences which were closely related (95% similarity) to that of the Mesorhizobium tianshanense type strain, indicating that they must have acquired the nodulation genes by a phenomenon of lateral gene transfer.