Canarian Populations Research Articles

Genetic population structure and dispersal in Atlantic Island caddisflies

SUMMARY 1. Population genetic structure of Wormaldia tagananana, a caddis with a narrow geographic range and endemic to the Canary Islands, was investigated by studying allozyme variation at 11 putative loci in five of the eight extant populations on Tenerife and La Gomera. Genetic variability, population structure and gene flow were compared with those reported previously in more widespread Trichoptera, particularly Canarian populations of the non‐endemic limnephilid Mesophylax aspersus, to examine the hypothesis that the Wormaldia, with its restricted range, would exhibit relatively little genetic variability and gene flow.2. Despite it being a narrow‐range island endemic, genetic variability in populations of W. tagananana is broadly similar to values reported for more widespread caddis.3. Significant genetic population structure was observed in W. tagananana (overall FST = 0.387), greater than that seen in M. aspersus and amongst the highest reported for lotic caddis to date. Several site‐ and island‐specific alleles were reported, providing further evidence for the relative isolation of individual Wormaldia populations.4. Significant deviations from Hardy–Weinberg equilibrium were found in four of five populations (overall FIS = 0.675). This could result from within‐locality population substructuring, or offspring within a reach being the product of a limited number of matings.5. This genetic evidence supports the hypothesis that the restricted range of W. tagananana is, at least in part, because of limited dispersal ability.

Biodiversity of Apis mellifera populations from Tenerife (Canary Islands) and hybridisation with East European races

The biodiversity of honeybee (Apis mellifera) populations from Tenerife (Canary Islands, Spain) has been assessed by restriction analysis of a mitochondrial non-coding intergenic region. Seventy-nine colonies were analysed from thirteen apiaries in six populations that have been kept from recent queen introduction. The length and restriction pattern of the PCR amplified products of the intergenic region identified four mitochondrial haplotypes. One of these haplotypes shows the same restriction pattern and composition of the intergenic region carried by honeybees belonging to the African lineage. Two haplotypes are characterised by a particular intergenic region found with high frequency in the Canarian populations. The haplotype representative of the East European honeybee lineage shows a frequency of 35%, thus indicating introduction of queen honeybees. The finding of this haplotype in Canarian honeybees suggests that hybridisation between the endemic Apis mellifera populations and imported bees is occurring in Tenerife.

RFLP Analysis in Canary Islands and North European Populations of Potato Cyst Nematodes (Globodera Spp.): Hybridization With Cloned Fragments

Four random probes from a Globodera pallida DNA library and one rDNA repeat probe from flax were used to highlight specific fragments in total DNA restricted with the endonucleases Bam HI, Eco RI, Eco RV, and Hind III, from 26 potato cyst nematode (PCN) populations (G. rostochiensis and G. pallida). The percentage similarity between species was low (%sm = 45.6). Cluster and principal coordinate analysis allowed us to hypothesise about the epidemiology of these populations. In the G. rostochiensis group, the populations representing pathotypes Ro2, Ro3, Ro4 and Ro5 may have been derived from the same introduction. Canarian populations R1, R2, R6, R7, and R10 were distinct from all the controls but R4 and R5 were close to the British Ro1 population. In the G. pallida group, the Luffness population was distinct from all others suggesting that it may represent a distinct introduction of PCN into the British Isles. Canarian population P9 had ten markers which were absent from the European control populations and it is possible that this population represents a distinct introduction of G. pallida into the Island of Tenerife.

Virulence of Canarian Populations of Potato Cyst Nematodes (Globodera Spp.)

The virulence spectrum of the potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, from the Island of Tenerife was assessed and compared with that found in Europe. Within the G. rostochiensis populations, all the Canarian populations, with the exception of one (R2), were avirulent to the H1 resistance gene and therefore belong to the virulence group Ro1/Ro4. Within the G. pallida populations from Tenerife it was apparent that the virulence gene which overcomes the H2 resistance gene is present only at a low frequency. Four populations, P4, P7, P8 and P13, would be classified as pathotype Pa1. A wide range of variation in virulence against clones derived from S. vernei was observed, indicating a continuum of virulence, rather than discrete pathotypes. There was some correlation between the fitness of the populations on the hosts derived from S. vernei and those with no resistance, but less correlation between virulence on the ex-S. vernei clones and one derived from ex-S. tuberosum ssp. andigena CPC 2802. The reproduction of the G. pallida populations on three ex-S. vernei clones also indicated that increasing resistance is predominantly additive and that the nature of virulence towards the three ex-S. vernei clones tested is similar. The differences in the multiplication of the populations on a particular clone may reflect the number of resistance genes present in the clone. A clone derived from ex-S. tuberosum ssp. andigena CPC 2802 was comparatively uniformly resistant to all the populations. Its resistance appears to be different from that in the ex-S. vernei clones and to interact with at least in part, different genes in G. pallida for virulence. The nature of resistance in the different clones tested and aspects concerning the epidemiology of potato cyst nematodes are discussed.

Biogeography of Cladophoropsis membranacea (Siphonocladales, Chlorophyta) as Revealed by Single Copy DNA Distances

Single copy DNA measurements were determined among isolates of Cladophoropsis membranacea from the Caribbean, Mauritania, the Canary Islands and the Red Sea using DNA-DNA hybridization. The genotypic relationships found amongst the Atlantic isolates demonstrate that the present day distribution pattern has been affected by jump dispersal. We have to reject strict trans-Atlantic vicariance and unimpeded gene flow through the Atlantic. The isolate from the Red Sea is more closely related to the Mauritanian/Caribbean isolates than to the Canarian one. This can be explained by jump dispersal around southern Africa. Any of these events should postdate the separation of the Canarian and Caribbean populations from which the isolates have been sampled.

Human Enzyme Polymorphism in the Canary Islands

The genetic polymorphism of eight red cell enzymes was analyzed in four population samples from the two easternmost islands of the Canary Archipelago. No heterogeneity was detected within the islands, but differences between them were of the same magnitude as those found between the islands and the Spanish mainland. The presence of the African G6PD-A+ and the rare G6PD-Gc alleles seems to be a characteristic of all Canarian populations studied.

Human enzyme polymorphism on the Canary Islands. I. Gran Canaria Island population.

Genetic polymorphism of seven red cell enzymes was examined in two Canary Island populations and in an Iberian peninsula sample. The more isolated insular population shows a considerable gene frequency heterogeneity when compared with the peninsular sample but both are within the range of European populations. The presence of certain rare alleles normally associated with blacks suggests an African component in the Canarian populations.