Variation in the subtropical group of Dactylis glomerata L.—1. Evidence from allozyme polymorphism

Notes on leaf micromorphology of the rare herbaceous bamboo Buergersiochloa bambusoides Pilg. (Olyreae, Poaceae) from New Guinea and its taxonomic implications

We present notes on the leaf micromorphology of Buergersiochloa bambusoides, a rare species from New Guinea and included in Buergersiochloinae, one of three subtribes of the herbaceous bamboos (tribe Olyreae). We used scanning electron microscopy and light microscopy to analyze the microcharacters of both adaxial and abaxial leaf surfaces. Within the Olyreae, saddle-shaped silica bodies in both the costal and intercostal zones are considered unique to Buergersiochloinae. Simple, circular and very small papillae are observed on the adaxial surface, and for the first time, branched papillae on the abaxial surface are observed in B. bambusoides. On the abaxial surface, there are papillae on long cells associated with the stomatal complexes. Bicellular microhairs are the only trichomes present and they are found almost exclusively on the abaxial surface. The saddle-shaped silica bodies are the most taxonomically important among the microcharacters observed on the leaf surface of B. bambusoides.

Analysis of the genetic diversity of the coastal and island endangered plant species Elaeagnus macrophylla via conserved DNA-derived polymorphism marker

The genetic diversity and genetic structure of five natural populations of the island and coastal endangered plant species Elaeagnus macrophylla were analyzed via conserved DNA-derived polymorphism molecular markers. A total of 289 discernible loci were obtained from 102 individuals via fifteen primers, and 100% of the loci were polymorphic. The observed number of alleles was 1.9654, and the effective number of alleles was 1.2604. Nei’s genetic diversity index was 0.1724 on average, and Shannon’s information index was 0.2869, indicating that Elaeagnus macrophylla had lower levels of genetic diversity than those reported for its continental relatives and other continental species. The average percentage of polymorphic loci was 42.1%, and the maximum and minimum were 80.97% and 14.88%, respectively, which were associated with the Nanji Island and Liugong Island populations, respectively. The populations of Elaeagnus macrophylla were highly differentiated. Cluster analysis revealed that the similarity between the tested samples was related to their geographical location, that the samples from the same island tended to cluster together, and that there was no cross-clustering between samples. The Nanji Island and Da Rushan populations differentiated into two subpopulations. Last, we detected no correlation between genetic distance and geographic distance between populations (Pearson’s correlation coefficient r = 0.256579, p-value = 0.8309).

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.

Chloroplast DNA variation in dactylis glomerata L. taxa endemic to the macaronesian islands

In the Dactylis glomerata infraspecific polyploid grass complex, restriction fragment length polymorphisms (RFLPs) of chloroplast DNA (cpDNA) were studied in diploid and tetraploid populations of several taxa endemic to Macaronesia (Madeira and the Canary islands) and in populations from the African and European continental areas closest to Macaronesia. Two chlorotypes, which differed by a single 290-bp length mutation, were observed in the Macaronesian and the continental populations. Chlorotype I, which is predominant in the whole D. glomerata complex, was found in the majority of continental populations. It was also observed in the most western Macaronesian islands, in the two diploid taxa endemic to the lowland scrub and the high elevation heath of Tenerife, respectively, and in tetraploids endemic to Madeira and La Palma. These island populations were growing under the influence of humid trade winds. Chlorotype II was found in the eastern part of the Archipelago (closer to Africa), which experienced subarid Mediterranean climate conditions, and in very few diploid and tetraploid Mediterranean populations growing at high elevation on the continent. This geographical and climatic distribution of chlorotype variation in Macaronesia is consistent with that reported previously for morphological, allozyme and phenolic variation in the same plant material. Chlorotype II was, however, also observed in tetraploid populations from La Gomera island and in one of the seven tetraploid populations analysed from Madeira, which all showed clearly subtropical characters for morphology, allozymes and phenolic compounds. This result suggests that cpDNA introgression has occurred more than once from the Mediterranean material into the subtropical one and may indicate that colonization between the mainland and islands, or among the islands, probably played a major role in the geographical pattern observed for that marker.