Population Structure and Growth Patterns of Opuntia echios var. gigantea along an Elevational Gradient in the Galípagos Islands1

Cacti growing in forests potentially experience growth limitation due to reduced light availability. To test this hypothesis, we studied the population structure of Opuntia echios var. gigantea at 15 sites on the south side of Isla Santa Cruz, Galípagos Islands, Ecuador. Populations were located in communities ranging from arid scrub at low elevations to closed‐canopy tropical dry forest at higher elevations. Ordination confirmed the existence of a strong elevation‐vegetation gradient. Opuntia abundance peaked at lower elevations (ca 30 m), with lower densities in closed‐canopy sites. For populations in scrub vegetation, density declined fairly regularly with plant height. Populations in forested sites had few plants of intermediate height, suggesting periodic recruitment. Scrub populations had random dispersion, while those in forests were aggregated. The change in spatial pattern may be related to a change in primary reproductive mode from asexual propagation via fallen fruits to propagation via fallen cladodes. Height was significantly correlated with stem diameter. Intercepts of these relationships increased toward higher elevations, probably in response to the increasing height of the surrounding canopy.     

On the general dynamic model of oceanic island biogeography

Aim To investigate the biological meaning of equations used to apply the general dynamic model (GDM) of oceanic island biogeography proposed by R. J. Whittaker, K. A. Triantis and R. J. Ladle. Location Analyses are presented for 17 animal groups living on the Aeolian Islands, a volcanic archipelago in the central Mediterranean, near Sicily. Methods In addition to the mathematical implementation of the GDM proposed by Whittaker, Triantis and Ladle, and termed here logATT² (, where S is species number or any other diversity metric, t is island age, A is island area, and a, b, c and d are fitted parameters), a new implementation based on the Arrhenius equation of the species–area relationship (SAR) is investigated. The new model (termed powerATT²) is: . For logATT² and powerATT² models, equations were developed to calculate (1) the expected number of species at equilibrium (i.e. when the island has reached maturity) per unit area (S_eq), and (2) the time required to obtain this value (t_eq). Whereas the intercept in the Gleason model (S = C + z log A) or the coefficient of the Arrhenius power model (S = CA^z) of the SAR can be considered measures of the expected number of species per unit area, this is not the case for the parameter a of the ATT² models. However, values of S_eq can be used for this purpose. The index of ‘colonization ability’ (CAB), calculated as the ratio , may provide a measure of the mean number of species added per unit area per unit time. Results Both ATT² models fitted most of the data well, but the powerATT² model was in most cases superior. Equilibrial values of species richness (S_eq) varied from c. 3 species km^?2 (reptiles) to 100 species km^?2 (mites). The fitted curves for the powerATT² model showed large variations in d, from 0.03 to 3. However, most groups had values of d around 0.2–0.4, as commonly observed for the z‐values of SARs modelled by a power function. Equilibration times ranged from about 170,000 years to 400,000 years. Mites and springtails had very high values of CAB, thus adding many more species per unit area per unit time than others. Reptiles and phytophagous scarabs showed very low values, being the groups that added fewest species per unit area per unit time. Main conclusions Values of equilibrial species richness per unit area are influenced by species biology (e.g. body size and ecological specialization). Theoretical and empirical evidence suggests that higher immigration rates should increase the z‐values of the Arrhenius model. Thus, in the same archipelago, groups with larger z‐values should be characterized by higher dispersal ability. Results obtained here for the parameter d conform to this prediction.     

Molecular phylogeny of the genus Pieris (Ericaceae) with special reference to phylogenetic relationships of insular plants on the Ryukyu Islands

Phylogenetic relationships within the genus Pieris (Ericaceae) were investigated based on the rbcL and matK genes along with five spacer sequences of chloroplast DNA to address questions regarding the phylogeography of the genus in association with insular plants on the Ryukyu Islands. The most parsimonious trees indicated that P. floribunda from eastern North America is a sister taxon to the remaining taxa examined, and suggested that the East Asian taxa examined are monophyletic. A morphologically cohesive group, section Pieris, was revealed to be paraphyletic. Within the East Asian clade, insular endemics from the Ryukyu Islands, Taiwan, and mainland Japan formed a sister group to P. formosa from the Himalayas and southern China. Our data suggest that the insular endemics of the Ryukyu Islands and Taiwan arose via allopatric divergence as a result of a paleogeographical land configuration of a landbridge during the early–middle Pleistocene in the Quaternary Period.     

Evolutionary biogeography of the terrestrial biota of the Marquesas Islands,one of the world's remotest archipelagos

Aim

Here I review phylogenetic studies concerning the biogeography of the Marquesas Islands, an oceanic hotspot archipelago in the Pacific Ocean formed <5.5 Ma, and compare patterns (particularly pertaining to colonization and diversification) within the archipelago to those reported from the Hawaiian and Society Islands.

Location

Marquesas Islands, French Polynesia (Pacific Ocean).

Methods

I reviewed 37 phylogenetic studies incorporating Marquesas‐endemic taxa. I asked the following questions: (a) where are the sister‐groups of Marquesas lineages distributed? (b) are Marquesas‐endemic “radiations” monophyletic or polyphyletic? (c) what major between‐island phylogeographic barriers are seen in the Marquesas? (d) what evidence exists for diversification within islands? (e) how old is the Marquesas biota compared to the archipelago's age? Finally, these patterns are compared with those seen in the Society Islands and Hawaii.

Results

Most Marquesan lineages have their closest known relatives on other Pacific plate archipelagos (particularly the Society, Hawaiian, and Austral islands). Most Marquesas‐endemic radiations are found to be monophyletic, and among‐island diversification appears to be common. There is limited evidence for within‐island diversification. Some radiations may be consistent with a weak progression rule in which younger lineages are on younger islands. Crown ages of no Marquesas radiations appear to be older than the age of the archipelago (with one exception).

Main conclusions

Diversification of the Marquesas biota resembles that of the Hawaiian Islands more than that of the Society Islands. Many radiations are monophyletic and some appear to diversify in parallel with the formation of the archipelago.

     

Two new species of the genusAmblyeleotris (Pisces: Gobiidae) from the Ryukyu Islands,Japan

Two new shrimp-associated gobies,Amblyeleotris yanoi sp. nov. andA. masuii sp. nov. are described on the basis of specimens from Iriomote-jima Island and Okinawa-jima Islands, Okinawa Prefecture, Japan.A. yanoi is distinguished from other members of the genus by the combination of the following characters: 14 anal fin soft rays, 19 pectoral fin rays, 97–103 longitudinal scales, a candle flame-shaped marking on the caudal fin, a very low membrane connecting the pelvic fins and absence of a ventral frenum.A. masuii differs from all other congeners by having 92–97 longitudinal scales, the length of the interpelvic connecting membrane relative to the longest pelvic fin ray (0.43–0.66), black blotches on the sides of the chin, and blue spots on the opercle and preopercle.     

Poa annua L. in Antarctic: searching for the source of introduction

The level of polymorphism, genetic variability and relatedness of a population of Poa annua L. from South Shetlands Islands was studied and compared with results obtained for populations from two potential sources of introduction (Argentina—Ushuaia and Poland—Dziekanów Leśny) using the amplified fragment length polymorphism (AFLP) approach. Five primer pairs used for AFLP profiling amplified 226 scoreable DNA fragments that were used for Clustral and Factorial analyses. The level of molecular variability among all individuals from all the analysed populations reaches 30%. Clustral and Factorial analyses show that all populations formed clear-cut uniform groups according to their locations. However, population from King George Island show high variability. High genetic diversity may be related with escalated human activity at the area of Arctowski Station, favouring introductions of P. annua from many different sources and by many different vectors.     

First record of a spawning aggregation for the tropical eastern Pacific endemic grouper Mycteroperca olfax in the Galapagos Marine Reserve

This study provides direct and indirect evidence of temporally and spatially consistent spawning aggregations for the grouper Mycteroperca olfax. Recently reported declines in population numbers, probably related to the direct targeting of aggregations by artisanal fishermen, highlight the urgent need for species‐specific management actions in the Galapagos Marine Reserve, such as minimum and maximum landing sizes, and the importance of protecting key aggregation sites with the declaration of no‐take areas and the establishment of total fishing bans during the reproductive season.     

Multilocus genetic diversity and historical biogeography of the endemic wall lizard from Ibiza and Formentera,Podarcis pityusensis (Squamata: Lacertidae)

Two monophyletic sister species of wall lizards inhabit the two main groups of Balearic Islands: Podarcis lilfordi from islets and small islands around Mallorca and Menorca and Podarcis pityusensis from Ibiza, Formentera and associated islets. Genetic diversity within the endangered P. lilfordi has been well characterized, but P. pityusensis has not been studied in depth. Here, 2430 bp of mtDNA and 15 microsatellite loci were analysed from P. pityusensis populations from across its natural range. Two main genetic groupings were identified, although geographical structuring differed slightly between the mtDNA and the nuclear loci. In general, individuals from islets/islands adjacent to the main island of Ibiza were genetically distinct from those from Formentera and the associated Freus islands for both mtDNA and the nuclear loci. However, most individuals from the island of Ibiza were grouped with neighbouring islets/islands for nuclear loci, but with Formentera and Freus islands for the mitochondrial locus. A time‐calibrated Bayesian tree was constructed for the principal mitochondrial lineages within the Balearics, using the multispecies coalescent model, and provided statistical support for divergence of the two main P. pityusensis lineages 0.111–0.295 Ma. This suggests a mid‐late Pleistocene intraspecific divergence, compared with an early Pleistocene divergence in P. lilfordi, and postdates some major increases in sea level between 0.4 and 0.6 Ma, which may have flooded Formentera. The program IMa2 provided a posterior divergence time of 0.089–0.221 Ma, which was similar to the multispecies coalescent tree estimate. More significantly, it indicated low but asymmetric effective gene copy migration rates, with higher migration from Formentera to Ibiza populations. Our findings suggest that much of the present‐day diversity may have originated from a late Pleistocene colonization of one island group from the other, followed by allopatric divergence of these populations. Subsequent gene flow between these insular groups seems likely to be explained by recent human introductions. Two evolutionary significant units can be defined for P. pityusensis but these units would need to exclude the populations that have been the subjects of recent admixture.     

On the identity of Riccia teneriffae S.W.Arnell (Marchantiophyta: Ricciaceae) and a note on R. cavernosa Hoffm. in the Canary Islands

Abstract

We revised both the holotype and an isotype of Riccia teneriffae S.W.Arnell 1962 and additionally revised our own collections of Riccia cavernosa Hoffm. 1795 from the Canary Islands. Since the types of R. teneriffae represent R. cavernosa, and the latter name precedes the former, R. teneriffae should be treated as a synonym of R. cavernosa. In the Canary Islands, R. cavernosa appears to be rare. It has been found on La Gomera, Gran Canaria, Lanzarote, and Tenerife. We report it as new to Fuerteventura. R. cavernosa inhabits ephemeral, thin layers of mud. Very rarely it occurs on basaltic pyroclasts. SEM images of spores are presented. The local distribution is mapped.