Polymorphic microsatellite loci for the Puerto Rican crested anole (<Emphasis Type="Italic">Anolis cristatellus</Emphasis>) and their amplification in related Puerto Rican species

We isolate six highly polymorphic microsatellite loci for the Puerto Rican crested anole (Anolis cristatellus) from a genomic library enriched for CA repeats. The number of alleles per locus ranged from 14 to 19, with levels of observed heterozygosity ranging from 0.60 to 0.73. Most of these loci were successfully cross-amplified in other members of the cristatellus species group (A. evermanni, A. gundlachi, A. krugi, A. stratulus), but levels of polymorphism were lower.     

Interactions between an introduced and indigenous coccinellid species at different prey densities

Coccinella septempunctata L. (Coleoptera: Coccinellidae), a Palearctic coccinellid, has established and rapidly spread throughout the United States. This quantitative examination of larval interactions between C. septempunctata and Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae), a Nearctic coccinellid, was conducted under controlled prey densities. Larvae of both coccinellid species are affected by a limited diet [one pea aphid per day Acyrthosiphon pisum (Harris) (Homoptera: Aphididae)] compared with an excess diet (>20 aphids per day). Larval survival decreased from 86 to 63% in C. maculata and from 84 to 33% in C. septempunctata; mean preimaginal developmental time increased from 20.6 to 26.7 days in C. maculata, and from 18.1 to 32.0 days in C. septempunctata. Additionally, on one aphid per day, mean adult weight was reduced from 12.39 to 9.79 mg in C. maculata, and from 39.57 to 14.44 mg in C. septempunctata. Interspecific interactions, favoring C. septempunctata over C. maculata at a␣low prey density (one aphid per day), take the form of␣reduced survival of C. maculata compared with C.␣septempunctata (14 versus 66%). Reduced survival of␣C. maculata may be the result of competition for aphids or intraguild predation by C. septempunctata on C.␣maculata. No interspecific interactions (measured as effects on larval survival, preimaginal developmental time, and adult weight) were observed between larvae of these two species at a high prey density (>20 aphids per predator per day). Received: 15 September 1997 / Accepted: 20 May 1998     

The visual ecology of Puerto Rican anoline lizards: habitat light and spectral sensitivity

The visual ecology of six closely related species of Puerto Rican anoline lizards was investigated and they were found to occupy four distinct habitat types in terms of light conditions: “full shade”, “partial shade”, “no shade”, and “forest canopy.”The habitats differed substantially in total radiance and irradiance as well as in the shape of the irradiance spectrum. The shape of the radiance spectrum was similar in all of the habitats. We used electroretinogram (ERG) flicker photometry to measure spectral sensitivity and found the curves for all six species to be similar. The spectral sensitivity peaked in the range 550–560 nm, which matched the peak in spectral radiance for all of the habitats. The shape of the spectral-sensitivity curve was similar to those of a number of other terrestrial vertebrates. We suggest that the convergence of the shape of the photopic ERG-determined spectral-sensitivity curve in many terrestrial vertebrates may, in part, be due to the fact that the background radiance of many terrestrial habitats is dominated by the reflectance spectrum of green vegetation which peaks at 550 nm. Accepted: 14 May 1997     

Egg-hatch phenology and intraguild predation between two mantid species

Relative timing of egg hatch between two cooccurring, congeneric mantids, Tenodera angustipennis and T. sinensis, was experimentally manipulated in replicated field enclosures to test the importance of intraguild predation to survivorship and development of T. angustipennis. T. angustipennis is normally smaller than its congener because of later egg-hatch. Delaying introduction of T. sinensis relative to normal egg hatch phenology reduced mortality for T. angustipennis, but did not affect its rate of development. The results indicate that intraguild predation by normally earlierhatching T. sinensis can be an important factor in the early life history of T. angustipennis, but that interspecific competition is not a strong selective factor in developmental asynchrony between these two species.     

Biology of the Mongoose (Herpestes javanicus) in a Rain Forest of Puerto Rico1

Ecological aspects of the mongoose (Herpestes javanicus) were studied in the Luquillo Mountains, a rain forest region in eastern Puerto Rico. Information was obtained by removal trapping of mongoose from grids placed in tree plantations, colorado and tabonuco forests. Trapping efficiency was two mongoose per 100 trap-days, suggesting mongoose abundance is low in wet montane forests of Puerto Rico. Sex ratio was biased (2.6:1) in favor of males. Body masses of male mongoose inhabiting rain forests of the Luquillo Mountains were larger than those in dry forests at Guánica (P < 0.0001). Stomach contents from 18 mongoose were examined, animal matter comprised 75 percent of the total food items encountered. Of these, 33 percent were from vertebrates. The food items most frequently encountered were lizards (Anolis spp.), centipedes (Scolopendra spp.), and cockroaches (Blatellidae).     

Chromosomes of some Puerto Rican flea beetles (Coleoptera: Chrysomelidae: Alticinae): multiple cytogenetic evolutionary tendencies in the neotropics

Meiotic chromosomes of 10 West Indian flea beetles with restricted distribution, including eight Puerto Rican endemics, were studied. Two species of the cosmopolitan Longitarsus resemble Old World congenerics in having meioformulae 13 + Xy and 14 + Xy, both with one pair of enlarged autosomes. One unidentified species of Aphthona seems to have achiasmatic meiosis. Among the Puerto Rican endemics, repeated fusions have produced low-numbered karyotypes in Homoschema latitarsum (2 + neoXY, now the lowest meioformula known for the Chrysomelidae) and Heikertingerella krugi (4 + neoXY). Three species of Aedmon have 18 + Xy_p as a result of a series of centric fissions from the Polyphagan ancestral condition of nine pairs. Phyllotrupes sp. (a new genus record for Puerto Rico, near P. acutangula ) and Pseudodisonycha portoricensis have 17 + Xy and 16 + Xy, respectively, plus a swarm of supernumerary chromosomes.     

Trophic interactions and habitat segregation between competing Daphnia species

Summary Two commonly coexisting species of Daphnia segregate by habitat in many stratified lakes. Daphnia pulicaria is mostly found in the hypolimnion whereas D. galeata mendotae undergoes diel vertical migration between the hypolimnion and the epilimnion. I examined how habitat segregation between these two potentially competing species might be affected by trophic interactions with their resources and predators by performing a field experiment in deep enclosures in which I manipulated fish predation, nutrient levels, and the density of epilimnetic Daphnia. The results of the experiment indicate that habitat use by D. pulicaria can be jointly regulated by competition for food from epilimnetic Daphnia and predation by fishes. Patterns of habitat segregation between the two Daphnia species were determined by predation by fish but not by nutrient levels: The removal of epilimnetic fish predators resulted in higher zooplankton and lower epilimnetic phytoplankton densities and allowed D. pulicaria to expand its habitat distribution into the epilimnion. In contrast, increased resource productivity resulted in higher densities of both Daphnia species but did not affect phytoplankton levels or habitat use by Daphnia. The two species exhibit a trade-off in their ability to exploit resources and their susceptibility to predation by fish. D. g. mendotae (the less susceptible species) may thus restrict D. pulicaria (the better resource exploiter) from the epilimnion when fish are common due to lower minimum resource requirements than those needed by D. pulicaria to offset the higher mortality rate imposed by selective epilimnetic fish predators. D. g. mendotae does not appear to have this effect in the absence of fish.     

Outcome of interspecific interactions among brown-rot and white-rot wood decay fungi

Abstract Interspecific mycelial interactions among brown-rot fungi resulted in either deadlock or replacement of one fungus by the other. Similarly, most of the brown-rot fungi deadlocked with some or all of the whitre-rot fungi tested, while a few were able to replace some of the white-rot fungi. The results indicate similarities in interspecific mycelial interactions among brown-rot fungi and between brown-rot and white-rot fungi. The results further suggest that some brown-rot fungi are capable of invading and occupying domains within white-rot fungal communities in decaying wood.     

Climatic stability and genetic divergence in the tropical insular lizard Anolis krugi,the Puerto Rican ‘Lagartijo Jardinero de la Montaña’

Two factors that can lead to geographic structuring in conspecific populations are barriers to dispersal and climatic stability. Populations that occur in different physiographic regions may be restricted to those areas by physical and/or ecological barriers, which may facilitate the formation of phylogeographic clades. Long‐term climatic stability can also promote genetic diversification, because new clades are more likely to evolve in areas that experience lesser climatic shifts. We conducted a phylogeographic study of the Puerto Rican lizard Anolis krugi to assess whether populations of this anole show genetic discontinuities across the species’ range, and if they do, whether these breaks coincide with the boundaries of the five physiographic regions of Puerto Rico. We also assessed whether interpopulation genetic distances in A. krugi are positively correlated with relative climatic stability in the island. Anolis krugi exhibits genetic structuring, but the phylogroups do not correspond to the physiographic regions of Puerto Rico. We used climatic reconstructions of two environmental extremes of the Quaternary period, the present conditions and those during the last glacial maximum (LGM), to quantify the degree of climatic stability between sampling locations. We documented positive correlations between genetic distances and relative climatic stability, although these associations were not significant when corrected for autocorrelation. Principal component analyses indicated the existence of climatic niche differences between some phylogeographic clades of A. krugi. The approach that we employed to assess the relationship between climatic stability and the genetic architecture of A. krugi can also be used to investigate the impact of factors such as the spatial distribution of food sources, parasites, predators or competitors on the genetic landscape of a species.     

An investigation of relationships between climate and dengue using a water budgeting technique

Climatic water budget indicators were used to assess intra- and interannual variations in dengue incidence for San Juan, Puerto Rico. Multivariate stochastic relationships between dengue and the water budget were developed to (1) determine and quantify the particular climatic measures and their associated lag periods related to dengue variations, and (2) assess their use for dengue prediction and initiation of emergency response procedures. Such a predictive model would be advantageous because it is based on reliable, easily obtained, and low-cost weather observations. Daily running averages of water budget variables over an 8-week period were related to daily running averages of unconfirmed dengue totals (1988–1993). Resultant models show that a variety of water budget and traditional climate measures over the full 8-week period are associated with dengue. The mean seasonal variation in dengue is highly related (R ²=88.1%) to the mean seasonal climate variation, with those thermal and energy variables immediately preceding the dengue response showing the strongest relationships. However, moisture variables, predominantly in the form of surplus, are more influential many weeks in advance. For the interannual model (R ²=44.1%), energy change, thermal change, and moisture variables are significant across the 8-week period, with moisture variables playing a stronger role than in the intraannual model. Standardisation substantially changes the importance and timing of the variables, and suggests that dengue during this period is more associated with the mean annual variation of climate than deviations from mean conditions. A dengue early-warning model (based on 5 weeks of climate data) was also developed to predict dengue incidence 3 weeks later. While this predictive model is not reliable as a sole predictor of dengue in San Juan, it may be useful as part of a multifaceted watch/warning system. Received: 5 September 2000 / Revised: 12 March 2001 / Accepted: 21 March 2001     

Competition between two congeneric stream gobies for habitat in southwestern Shikoku, Japan

Competition between two congeneric gobies, Rhinogobius sp. LD (large-dark type) and CB (cross-band type), for habitat was studied in a tributary of the Shimanto River, southwestern Shikoku, Japan. Habitat use by CB, measured by water depth, current velocity, and substrate, was compared between before and after the removal of LD. After the removal of LD, CB shifted their habitat use to coarser substrates than previously, suggesting a release from effects of LD. This result supports a hypothesis from our previous study that habitat partitioning between CB and LD is a consequence of interference effects of LD on CB.     

Intra- and interspecific cohabitation of scorpions in the field and the effect of density, food, and shelter on their interactions

Scorpion cohabitation was studied qualitatively and quantitatively for several years in the field and in controlled experimental conditions in the laboratory. In the field, several cases were recorded of scorpions sharing the same shelter, either intra- or interspecifically. Intraspecific cohabitation was more prevalent than interspecific cohabitation. Among the five scorpion species studied here, Compsobuthus werneri judaicus shows the highest degree of sociality and aggregates both intra- and interspecifically. Leiurus quinquestriatus was never observed to cohabit interspecifically. Both Buthotus judaicus and C. werneri judaicus shared shelters with other scorpions more frequently during the wet season, whereas Nebo hierichonticus and Scorpio maurus fuscus cohabitated more often during the dry season. Under controlled laboratory conditions, density and availability of either food or shelter appear to be significant in facilitating cohabitation, even in the more aggressive species. Received: April 28, 1999 / Accepted: July 30, 1999     

Competitive interactions between two successful molluscan invaders of freshwaters: an experimental study

The New Zealand mud snail Potamopyrgus antipodarum (Hydrobiidae) and the pulmonate Physella acuta (Physidae) have invaded freshwaters in many parts of the world and become established. They co-exist in many streams, lakes and ponds in New Zealand, often at high densities. In the present study the effects of intraspecific- and interspecific interactions between the two species on growth and reproductive output were examined in laboratory mesocosms. In 30-day experiments, growth of Potamopyrgus antipodarum was lower in high density treatments than controls providing evidence for competition at higher densities of both snail species. No competitive effect was obtained for Physella acuta when controls were compared with high-density treatments, but growth was reduced at high densities of conspecifics. Numbers of juveniles released by Potamopyrgus antipodarum in 40 day trials declined at high snail densities and were lowest at high densities of conspecifics. Egg production by Physella acuta was also reduced at high snail densities. However, when the two species were kept together at equal densities (total snail density twice that of controls), egg production by Physella acuta was significantly higher than in all other treatments, suggesting facilitation by the congenor. Lastly, in a 10-day experiment, Physella acuta grew faster in water conditioned by Potamopyrgus antipodarum than in Physa-conditioned water, whereas Potamopyrgus antipodarum showed no growth response to Physella-conditioned water. Overall, our results indicate that growth and reproductive output of both snail species are influenced more by the density of conspecifics than the presence and density of the other species. The successful co-existence of the two species in New Zealand freshwaters therefore may be a reflection, at least in part, of few competitive interactions between them.     

Population and microhabitat effects of interspecific interactions on the endangered Andalusian toothcarp (A<Emphasis Type=Italic>phanius baeticus</Emphasis>)

The Andalusian toothcarp, Aphanius baeticus, is a critically endangered cyprinodontid species, with only nine known extant populations. Although not yet studied in the field, the distribution and abundance of Andalusian toothcarp are thought to be strongly influenced by interspecific interactions. We analysed the abundance and microhabitat use of Andalusian toothcarp in two water courses, one in which several other fish species occurred (sympatric site) and one hypersaline stream in which toothcarp was the only species present (allopatric site). Fish were sampled using plastic minnow traps and results were analysed separately for three size categories. Toothcarps were clearly more abundant in the allopatric population than in the sympatric one, though the difference was less apparent in the smallest size category. In coexistence with other species, toothcarp occupied shallower microhabitats, but in both sites in the absence of shelter fish selected deeper positions than in its absence. While in the sympatric site sheltered microhabitats were used predominately by small individuals, in the allopatric ones they were used by larger ones. Observed patterns strongly suggest that predation is the main mechanism involved in the differences in abundance and microhabitat use between sites. Our results confirm that the presence or absence of coexisting species is an important habitat feature for Andalusian toothcarp populations.     

Natural enemy diversity and biological control: Making sense of the context-dependency

Numerous studies have demonstrated that diverse predator assemblages can be more effective at controlling prey populations. Yet, other studies have shown no effect of predator diversity on prey mortality, or even negative effects (for example due to intraguild predation or interference). Much research emphasis has been placed on the traits of predators that maximise functional complementarity. However, comparatively less attention has been paid to the traits of the prey or habitat that may maximise predator diversity effects, even though there must be a variety of prey niches available to be partitioned in order for niche complementarity to occur. Following this logic, we review six hypotheses for when diverse enemy assemblages should be most effective: when 1) prey communities are diverse; 2) prey have complex life cycles; 3) prey are patchily distributed in space or time; 4) studies are conducted at larger spatial and temporal scales; 5) plant structures are complex; 6) prey are abundant. Many of these hypotheses lack direct tests, particularly in agricultural systems, but we find little or no direct or indirect support for hypotheses 1, 4, 5 and 6. However, previous work does provide some support for hypotheses 2 and 3. We discuss methods to test these hypotheses directly, and suggest that natural enemy diversity may only benefit the biological control of arthropods in heterogeneous systems.     

Development and use of molecular diagnostic tools to determine trophic links and interspecific interactions in aphid-parasitoid communities in Hawaii

There has been much debate regarding the impact of parasitoid competition and hyperparasitism on the successful biological control of aphid pests. Difficulty in the evaluation of interspecific interactions and trophic links using conventional rearing and dissection methods has prevented a deeper understanding of such relationships. The analysis of trophic links in the parasitoid community associated with the melon aphid (Aphis gossypii) in Hawaii provides a unique opportunity to assess complex interactions that occur in a system where all of the aphids and parasitoids have been introduced. Here, we developed and applied multiplex PCR assays to investigate the occurrence of in-host competition between parasitoids and/or hyperparasitoids on melon aphids collected from fields of Colocasia esculenta. To fully document the parasitoid-hyperparasitoid community within A. gossypii, both live and mummified aphids were examined. A total of 818 live and 245 mummified aphids were analyzed using the multiplex assays, with congruent rearing of over 600 mummified aphids serving as a basis for qualitative comparisons in terms of species composition and trophic linkages. The rearing and the DNA methods showed similar trends, with sharp declines in one parasitoid species followed by sharp increases in another during the course of the season. Molecular analyses revealed that hyperparasitism and multiparasitism of live aphids is remarkably low, whereas hyperparasitism of mummified aphids was extraordinarily high in both rearing and molecular analyses. In comparison to reared samples, molecular analysis of the parasitoid community was more complete and permitted the identification of previously unknown or unconfirmed trophic linkages. The potential of this approach in future studies on the biological control of aphids in Hawaii, particularly in light of new parasitoid introductions, is discussed.     

Predator-prey interactions between two amphibian species: effects of insecticide exposure

The presence of environmental contaminants may alter predator-prey interactions among aquatic species by altering activity levels of predators or prey, or by altering predator avoidance behavior. The outcome of a predatory encounter may be dependent upon whether both species are exposed to a contaminant simultaneously, or whether exposure occurs only in one of the species. In a laboratory experiment, I used the insecticide carbaryl to examine predation of southern leopard frog tadpoles (Rana sphenocephala) by adult red-spotted newts (Notophthalmus viridescens) under four conditions: both tadpoles and newts exposed, neither tadpoles nor newts exposed, and either newts or tadpoles only exposed. After one hour, exposed newts consumed half as many tadpoles as non-exposed newts. Carbaryl potentially affected newt activity enough to reduce time spent searching for prey, or may have altered the speed and coordination necessary to capture tadpoles. After six hours, non-exposed and exposed newts consumed similar numbers of tadpoles, most likely indicating recovery from exposure. After 24 h, predation rates were lowest when both newts and tadpoles were simultaneously either exposed or not exposed, and were greatest when newts and tadpoles were not exposed simultaneously. This study suggests that when tadpoles and newts are exposed to a sublethal level of a contaminant simultaneously, that predation rates do not differ from those observed under natural conditions, but exposure of either predator or prey at different times can disrupt predator-prey dynamics. This revised version was published online in August 2006 with corrections to the Cover Date.