Javier Francisco-Ortega

Plant genetic diversity in the Canary Islands: a conservation perspective

The Canary Islands are an Atlantic volcanic archipelago with a rich flora of ∼570 endemic species. The endemics represent ∼40% of the native flora of the islands, and ∼20% of the endemics are in the E (endangered) category of the International Union for Conservation of Nature. A review of allozyme variation in 69 endemic species belonging to 18 genera and eight families is presented. The average species-level genetic diversity (H(T)) at allozyme loci is 0.186, which is twice as high as the mean reported for endemics of Pacific archipelagos. Possible factors contributing to this higher diversity are discussed, but the reasons remain obscure. An average of 28% of the allozyme diversity within species resides among populations, indicating a high level of interpopulational differentiation. Studies of reproductive biology indicate that many of the endemic species are outcrossers. The high total diversity within species, the relatively high differentiation among populations, and the outcrossing breeding systems have implications for species conservation. Decreased population sizes in outcrossing species would promote biparental inbreeding and increase inbreeding depression. The relatively high proportion of allozyme diversity among populations indicates that the most effective strategy for preserving genetic variation in species is to conserve as many populations as possible. The genetic diversity in many Canary Island endemics is endangered by: (1) overgrazing by introduced animals, such as barbary sheep, goats, mouflons, rabbits, and sheep; (2) interspecific hybridization following habitat disturbance or planting of endemics along roadsides or in public gardens; (3) competition with alien plant species; and (4) decline of population size because of urban development and farming.

Relationships of the Macaronesian and Mediterranean floras: molecular evidence for multiple colonizations into Macaronesia and back-colonization of the continent in Convolvulus (Convolvulaceae)

A molecular phylogenetic analysis of the Macaronesian endemic species of Convolvulus was undertaken using data from the nuclear ribosomal internal transcribed spacer (ITS) regions. The results of the analysis support two introductions into Macaronesia from distantly related clades within Convolvulus and a subsequent back-colonization to the continent from within one of the clades. Hypothesized relationships between Macaronesian species and New World taxa and between the Canarian endemic C. caput-medusae and the Moroccan C. trabutianus are refuted. Both Macaronesian clades are shown to have Mediterranean sister groups although one is predominantly western Mediterranean and the other predominantly eastern Mediterranean in distribution. The patterns of colonization into Macaronesia demonstrated by Convolvulus and also by other multiple colonizing genera conform to either a pattern of phylogenetic distinctiveness or a checkerboard distribution of island lineages. Both are consistent with the hypothesis that niche preemption is responsible for the limited number of colonizations into the region. A review of sister group relationships demonstrates that, in common with Convolvulus, most Macaronesian groups have sister groups distributed in the near-continent (i.e., western Mediterranean). Disjunct sister group relationships (including Eastern Mediterranean disjunctions) occur in only 18% of groups.

Phylogenetics and Evolution of the Macaronesian Clade of Crassulaceae Inferred from Nuclear and Chloroplast Sequence Data

Abstract The Macaronesian clade of Crassulaceae comprises four genera (Aichryson, Aeonium, Greenovia, and Monanthes) that are largely endemic to Macaronesia, a region encompassing the Azores, Madeira, and the Cape Verde, Canary, and Salvage Islands. The monophyly of this clade has been supported by recent family-level phylogenetic analyses; however, the relationships within the clade remain uncertain. To resolve relationships within the Macaronesian clade, we sequenced several chloroplast DNA regions (matK and the trnL-trnF and psbA-trnH spacer regions) and the nuclear rDNA ITS region. Parsimony analyses of separate ITS and cpDNA data sets recover three major clades, corresponding to Aichryson, the perennial species of Monanthes, and Aeonium (including Greenovia). Congruence tests revealed significant heterogeneity between the ITS and cpDNA data sets. Comparison of the topologies resulting from analyses of these separate data sets indicated five instances of incongruence between the ITS and cpDNA that may be the result of cpDNA capture events. Those five cpDNA sequences that appear to be the result of hybridization were removed, and a combined cpDNA/ITS data set was constructed and analyzed. Parsimony analyses of this combined data set again resolve three major clades that correspond to Aichryson, Monanthes, and Aeonium (including Greenovia); however, the combined analyses provide greater resolution and higher internal support than the analyses of the separate data sets. Given this estimate of phylogeny, the Macaronesian clade most likely evolved from herbaceous, continental ancestors; the woody habit evolved once in Aichryson tortuosum and again in the ancestor of the Aeonium clade. Combined analyses of cpDNA and ITS for a large sampling of the Macaronesian Crassulaceae also confirms recent conclusions that Aeonium originated in Macaronesia and not in Africa and that the east African species, A. leucoblepharum, is of recent origin and represents long-distance dispersal from Macaronesia to Africa. Communicating Editor: Paul Wilson

Molecular Phylogenetic Insights on the Origin and Evolution of Oceanic Island Plants

The floras and faunas of oceanic islands have fascinated evolutionary biologists since the time of Darwin (1859) and Wallace (1880). Questions that first arose about island life are among those still being addressed today: How did terrestrial organisms come to exist on remote islands? What ancestors gave rise to island lifeforms? Why are so many insular species unique and different from those of other islands and continental settings? For Darwin, such questions about organisms of the Galapagos archipelago were helpful in formulating his ideas about evolutionary change.

Phylogenetic relationships and evolution of Crassulaceae inferred from matK sequence data.

Chloroplast gene matK sequence data were used to estimate the phylogeny of 112 species of Crassulaceae sampled from 33 genera and all six recognized subfamilies. Our analyses suggest that five of six subfamilies recognized in the most recent comprehensive classification of the family are not monophyletic. Instead, we recovered a basal split in Crassulaceae between the southern African CRASSULA: clade (Crassuloideae) and the rest of the family (Sedoideae). These results are compatible with recent studies of cpDNA restriction site analyses. Within Sedoideae, four subclades were also recovered: KALANCHOE:, Leucosedum, Acre, and AEONIUM:; evidence also exists for a TELEPHIUM: clade and SEMPERVIVUM: clade. The genus SEDUM: is highly polyphyletic with representatives spread throughout the large Sedoideae clade. Sympetaly and polymerous flowers have arisen multiple times in Crassulaceae and thus are not appropriate characters upon which to base subfamilial limits, as has been done in the past. One floral character, haplostemy, appears to be confined to the well-supported CRASSULA: clade. Our analyses suggest a southern African origin of the family, with subsequent dispersal northward into the Mediterranean region. From there, the family spread to Asia/eastern Europe and northern Europe; two separate lineages of European Crassulaceae subsequently dispersed to North America and underwent substantial diversification. Our analyses also suggest that the original base chromosome number in Crassulaceae is x = 8 and that polyploidy has played an important role in seven clades. Three of these clades are exclusively polyploid (SEMPERVIVUM: clade and two subclades within the KALANCHOE: and AEONIUM: clades), whereas four (Crassula, Telephium, Leucosedum, and ACRE: clades) comprise both diploid and polyploid taxa. Polyploidy is particularly rampant and cytological evolution especially complex in the ACRE: clade.

Origin and evolution of the endemic genera of Gonosperminae (Asteraceae: Anthemideae) from the Canary Islands: evidence from nucleotide sequences of the internal transcribed spacers of the nuclear ribosomal DNA

The Gonosperminae (Asteraceae) are composed of three genera endemic to the Canary Islands (GONOSPERMUM: Less., and LUGOA: DC.) and southern Africa (INULANTHERA: Källersjö), and they are considered an example of a floristic link between these two regions. Phylogenetic analyses of ITS sequences reveal that the Canarian genera are not sister to INULANTHERA: and do not support the monophyly of the Gonosperminae. These results, coupled with previous phylogenetic studies of other groups, suggest that many of the putative biogeographic links between Macaronesia and southeast Africa need to be evaluated by rigorous phylogenetic analyses. INULANTHERA: forms part of the basal southern African radiation of the Anthemideae, and therefore it is closely related to other taxa from this region. Maximum likelihood and weighted parsimony analyses support a monophyletic group in the Canary Islands, that includes LUGOA:, Gonospermum, and three TANACETUM: species endemic to the island of Gran Canaria. Bootstrap support for the monophyly of this Canarian group is weak, and it collapses in the strict consensus tree based on unweighted parsimony. LUGOA: is nested within Gonospermum, and both interisland colonization among the western islands of La Gomera, El Hierro, La Palma and Tenerife, and radiation on the central island of Gran Canaria have been the major patterns of species diversification for these Canarian endemics.

Biogeography and Breeding System Evolution of the Woody Bencomia Alliance (Rosaceae) in Macaronesia Based on ITS Sequence Data

Abstract The origin of the flora of the Macaronesian archipelagos has been a subject of controversy for over a century with the traditional opinion asserting that it is a relictual fragment of a widespread Tertiary subtropical European flora. A phylogenetic investigation of the three Macaronesian genera of the Bencomia alliance (Bencomia, Dendriopoterium, and Marcetella) using sequence data from the nuclear rDNA Transcribed Spacer region (ITS) has provided evidence relevant to the origin of the Macaronesian flora and the evolution of morphological characters of interest to students of island biology. In the ITS phylogeny, the Bencomia alliance, Sarcopoterium, a monotypic genus of the eastern Mediterranean, and Sanguisorba ancistroides, also a Mediterranean species, form a clade that is sister to the Eurasian Sanguisorba minor. These relationships contradict the relictual hypotheses and show that the endemic Macaronesian Rosaceae are sister to Mediterranean Sanguisorbeae. The data also contradict a recent placement of Dendriopoterium and Marcetella together in a subgenus of Sanguisorba. The ITS tree demonstrates that dioecy evolved in the islands from a continental monoecious or gynomonecious ancestor and that there has been an increase in plant size and woodiness compared to continental relatives rather than the decrease suggested by previous workers. Communicating Editor: Matt Lavin

Chloroplast DNA evidence for the roles of island colonization and extinction in Tolpis (Asteraceae: Lactuceae)

Tolpis consists of ∼13 species native to Africa, Europe, and Macaronesia, with at least one species endemic to each of the four major archipelagos of the Azores, Madeira Islands, Canary Islands, and Cape Verde Islands. All but two of these species develop woody stems by maturity. Chloroplast DNA restriction site variation was analyzed for all species of Tolpis and four outgroups in order to understand the patterns of island colonization and evolution of woodiness in this genus. Parsimony analyses revealed a strongly supported monophyletic Tolpis. Within the genus, the following three well-supported groups were detected: all species from the Canary Islands and Cape Verde Islands, both Azorean species, and both continental species. The Canary Island/Cape Verde clade was sister to the two continental species, and the Azorean clade was sister to this group. The two Madeiran species of Tolpis occupied the basalmost positions within the genus. When biogeography was mapped onto this phylogeny, nine equally parsimonious reconstructions (five steps each) of dispersal history were detected, which fell into two groups: eight reconstructions implied that Tolpis colonized Madeira from the continent, followed by continental extinction and subsequent continental recolonization, while one reconstruction implied that Tolpis colonized Macaronesia four times. Two of the reconstructions involving continental extinction required the least amount of overall dispersal distance. The cpDNA phylogeny also suggests that woodiness arose in the common ancestor of all extant Tolpis, followed by two independent reversals to an herbaceous habit. Assuming that one of the eight reconstructions favoring continental extinction and recolonization is true, our results suggest that Tolpis may represent the first documented example of a woody plant group in Macaronesia that has recolonized the mainland in herbaceous form.

Phylogeny of the Macaronesian endemic Crambe section Dendrocrambe (Brassicaceae) based on internal transcribed spacer sequences of nuclear ribosomal DNA

The 14 species of Crambe L. sect. Dendrocrambe DC. (Brassicaceae) form a monophyletic group endemic to the Canary and Madeira archipelagos. Both parsimony and maximum likelihood analyses of sequence data from the two internal transcribed spacer regions of nuclear ribosomal DNA were used to estimate phylogenetic relationships within this section. These analyses support the monophyly of three major clades. No clade is restricted to a single island, and therefore it appears that inter-island colonization has been the main avenue for speciation in these two archipelagos. The two species endemic to Fuerteventura (C. sventenii) and Madeira (C. fruticosa) comprise a clade, providing the first evidence for a floristic link between the Eastern Canary Islands and the archipelago of Madeira. Both maximum likelihood and weighted parsimony analyses show that this clade is sister to the two other clades, although bootstrap support for this relationship is weak. Parsimony optimizations of ecological zones and island distribution suggest a colonization route from the low-altitude areas of the lowland scrub toward the high-elevation areas of the laurel and pine forests. In addition, Tenerife is likely the ancestral island for species endemic to the five westernmost islands of Gran Canaria, La Gomera, El Hierro, La Palma, and Tenerife.

Origin of Macaronesian Sideritis L. (Lamioideae: Lamiaceae) inferred from nuclear and chloroplast sequence datasets.

Sideritis L. (Lamiaceae) comprises approximately 150 species of annuals and perennials distributed chiefly in the Mediterranean region. The majority of the species belong to the continental subgenus Sideritis which is divided into two perennial (Sideritis and Empedoclea) and two annual (Hesiodia and Burgsdorfia) sections. Twenty-three species are woody perennials endemic to the Macaronesian archipelagos of Madeira and the Canary Islands. In an effort to determine the continental origin of the insular group, we constructed independent phylogenies comprising sequence data from both chloroplast and nuclear markers. Sampling included 7 island taxa drawn from the Macaronesian subgenus Marrubiastrum and 25 continental taxa representing all four sections of subgenus Sideritis. Subgenus Marrubiastrum and the two continental perennial sections form well-supported monophyletic groups in both individual and combined analyses. The annual sections are not monophyletic in any analysis; further sampling of annual taxa is needed to resolve these relationships. All analyses identified Sideritis cossoniana, an annual species from Morocco, as the closest continental relative of the Macaronesian group. This contrasts with the hypothesis of earlier workers who suggested that the insular taxa were most closely related to eastern Mediterranean species of the genus. The phylogenies also demonstrate a distinct increase in woodiness among the Macaronesian species relative to their continental congeners, providing further support for the secondary nature of woodiness in island plants.