Deep intra‐island divergence of a montane forest endemic: phylogeography of the Puerto Rican frog Eleutherodactylus portoricensis (Anura: Eleutherodactylidae)

Aim Hypotheses proposed for lineage diversification of tropical montane species have rarely been tested within oceanic islands. Our goal was to understand how basin barriers and Pleistocene climatic fluctuations shaped the distribution of diversity in Eleutherodactylus portoricensis (Eleutherodactylidae), a frog endemic to the montane rain forests of Puerto Rico. Location The north‐eastern (Luquillo) and south‐eastern (Cayey) mountains of Puerto Rico. Methods We generated mitochondrial DNA (mtDNA) control region sequences (c. 565 bp) from 144 individuals of E. portoricensis representing 16 localities, and sequenced 646 bp of cytochrome b and 596 bp of nuclear DNA (nDNA) rhodopsin exon and intron 1 from a subset of individuals. We conducted a phylogenetic analysis on the mtDNA sequence data and explored population substructure with maximum parsimony networks, a spatial analysis of molecular variance, and pairwise F_ST analysis. Coalescent simulations were performed to test alternative models of population divergence in response to late Pleistocene interglacial periods. Historical demography was assessed through coalescent analyses and Bayesian skyline plots. Results We found: (1) two highly divergent groups associated with the disjunct Luquillo and Cayey Mountains, respectively; (2) a shallow mtDNA genetic discontinuity across the La Plata Basin within the Cayey Mountains; (3) phylogeographic congruence between nDNA and mtDNA markers; (4) divergence dates for both mtDNA and nDNA pre‐dating the Holocene interglacial (c. 10 ka), and nDNA suggesting divergence in the penultimate interglacial (c. 245 ka); and (5) historical demographic stability in both lineages. Main conclusions The low‐elevation Caguas Basin is a long‐term barrier to gene flow between the two montane frog populations. Measures of genetic diversity for mtDNA were similar in both lineages, but lower nDNA diversity in the Luquillo Mountains lineage suggests infrequent dispersal between the two mountain ranges and colonization by a low‐diversity founder population. Population divergence began prior to the Holocene interglacial. Stable population sizes over time indicate a lack of demonstrable demographic response to climatic changes during the last glacial period. This study highlights the importance of topographic complexity in promoting within‐island vicariant speciation in the Greater Antilles, and indicates long‐term persistence and lineage diversification despite late Pleistocene climatic oscillations.     

Sea level,topography and island diversity: phylogeography of the Puerto Rican Red‐eyed Coquí, Eleutherodactylus antillensis

Quaternary climatic oscillations caused changes in sea level that altered the size, number and degree of isolation of islands, particularly in land‐bridge archipelagoes. Elucidating the demographic effects of these oscillations increases our understanding of the role of climate change in shaping evolutionary processes in archipelagoes. The Puerto Rican Bank (PRB) (Puerto Rico and the Eastern Islands, which comprise Vieques, Culebra, the Virgin Islands and associated islets) in the eastern Caribbean Sea periodically coalesced during glaciations and fragmented during interglacial periods of the quaternary. To explore population‐level consequences of sea level changes, we studied the phylogeography of the frog Eleutherodactylus antillensis across the archipelago. We tested hypotheses encompassing vicariance and dispersal narratives by sequencing mtDNA (c. 552 bp) of 285 individuals from 58 localities, and four nuDNA introns (totalling c. 1633 bp) from 173 of these individuals. We found low support for a hypothesis of divergence of the Eastern Islands populations prior to the start of the penultimate interglacial c. 250 kya, and higher support for a hypothesis of colonization of the Eastern Islands from sources in eastern Puerto Rico during the penultimate and last glacial period, when a land bridge united the PRB. The Río Grande de Loíza Basin in eastern Puerto Rico delineates a phylogeographic break. Haplotypes shared between the PRB and St. Croix (an island c. 105 km south‐east of this archipelago) likely represent human‐mediated introductions. Our findings illustrate how varying degrees of connectivity and isolation influence the evolution of tropical island organisms.     

Response to simultaneous dehydration and thermal stress in three species of Puerto Rican frogs

Summary The response to simultaneous temperature and dehydration stress was examined in three species of Puerto Rican frogs.Eleutherodactylus antillensis is found primarily in hot, arid grasslands at low altitudes.Eleutherodactylus portoricensis is restricted to cool, forested montane habitats above 300 m.Eleutherodactylus coqui occurs in both the lowlands and the highlands. The physiological tolerance of the frogs to temperature was measured at 20, 25, and 30°C at various levels of dehydration using an index derived from jumping performance. Although jump distance of fully hydratedE. antillensis was unaffected by temperature, this species tolerated significantly more dehydration at high temperatures than low.Eleutherodactylus portoricensis died at 30°C, but in this species both distance jumped and dehydration tolerance were unaffected by lower temperatures. Distance jumped byE. coqui increased with increasing temperature, but tolerance of dehydration remained unchanged.Eleutherodactylus coqui was less tolerant of high temperatures thanE. antillensis but more tolerant thanE. portoricensis.Abbreviations DT dehydration tolerance - SVL snout vent length     

Molecular anatomy of the developing limb in the coquí frog,Eleutherodactylus coqui

The vertebrate limb demonstrates remarkable similarity in basic organization across phylogenetically disparate groups. To gain further insight into how this morphological similarity is maintained in different developmental contexts, we explored the molecular anatomy of size‐reduced embryos of the Puerto Rican coquí frog, Eleutherodactylus coqui. This animal demonstrates direct development, a life‐history strategy marked by rapid progression from egg to adult and absence of a free‐living, aquatic larva. Nonetheless, coquí exhibits a basal anuran limb structure, with four toes on the forelimb and five toes on the hind limb. We investigated the extent to which coquí limb bud development conforms to the model of limb development derived from amniote studies. Toward this end, we characterized dynamic patterns of expression for 13 critical patterning genes across three principle stages of limb development. As expected, most genes demonstrate expression patterns that are essentially unchanged compared to amniote species. For example, we identified an EcFgf8‐expression domain within the apical ectodermal ridge (AER). This expression pattern defines a putatively functional AER signaling domain, despite the absence of a morphological ridge in coquí embryos. However, two genes, EcMeis2 and EcAlx4, demonstrate altered domains of expression, which imply a potential shift in gene function between coquí frogs and amniote model systems. Unexpectedly, several genes thought to be critical for limb patterning in other systems, including EcFgf4, EcWnt3a, EcWnt7a, and EcGremlin, demonstrated no evident expression pattern in the limb at the three stages we analyzed. The absence of EcFgf4 and EcWnt3a expression during limb patterning is perhaps not surprising, given that neither gene is critical for proper limb development in the mouse, based on knockout and expression analyses. In contrast, absence of EcWnt7a and EcGremlin is surprising, given that expression of these molecules appears to be absolutely essential in all other model systems so far examined. Although this analysis substantiates the existence of a core set of ancient limb‐patterning molecules, which likely mediate identical functions across highly diverse vertebrate forms, it also reveals remarkable evolutionary flexibility in the genetic control of a conserved morphological pattern across evolutionary time.     

Isolation of Histoplasma capsulatum from tissues of bats captured in the Aguas Buenas Caves,Aguas Buenos,Puerto Rico

Of 30 bats belonging to four species, only one species, Brachyphylla cavernarum, yielded positive for Histoplasma capsulatun. Bats were collected at the Aguas Buenas Caves in Puerto Rico. The other species are: Artibeus jamaicensis, Monophyllus redmani portoricensis, and Erophylla bibombifrons; these resulted negative for the fungus.     

Dietary overlap between the invasive coquí frog (<Emphasis Type="Italic">Eleutherodactylus coqui</Emphasis>) and the Hawaiian hoary bat (<Emphasis Type="Italic">Lasiurus cinereus semotus</Emphasis>) on the Island of Hawai’i

The invasive coquí frog is a likely insectivorous competitor to the native Hawaiian hoary bat. The frog is a sit-and-wait predator native to Puerto Rico, but it has the capacity for producing dense populations in its invasive range and the potential to reduce arthropod populations, including aerial arthropods in the orders Coleoptera, Lepidoptera and Isoptera, which are primary food sources of the Hawaiian hoary bat. Dietary analysis of the coquí frog showed that aerial insects made up 33.8 % of the diet. The dietary similarity of the bat and frog was relatively low (Pianka index = 0.25), however, coquí frogs consumed a wide range of juvenile flying insects. Population densities of coquí frogs at two low elevation sites were projected to range from 750 to 14,000 individuals/hectare, and could consume an estimated 1500–19,000 aerial insects/hectare/night, or nearly 90.6 % of all available aerial insects/hectare. Although direct competition between coquí frogs and Hawaiian hoary bats was not confirmed, the coquí frogs could reduce available prey for bats in newly invaded upland sites where bats appear to be more selective of prey species among available aerial insects.     

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).     

A review of the net-winged midges (Diptera: Blephariceridae) of the West Indies,with description of a new species from Puerto Rico

ABSTRACT

The Caribbean blepharicerid fauna comprises three described species: Paltostoma palominoi Hogue and Garces, 1990, found in eastern Cuba; P. agyrocincta Curran, 1927, widespread in Puerto Rico; and P. schineri Williston, 1896, which occupies most major islands of the Lesser Antilles. In this paper, we describe P. portoricensis Hogue and Courtney, sp. n., a second species from Puerto Rico. We also provide keys to adults, pupae, and larvae of known Caribbean species, re-describe P. argyrocincta and P. schineri, and present a brief discussion of the bionomics and phylogenetic affinities of the net-winged midge fauna.     

Tropical understory herbaceous community responds more strongly to hurricane disturbance than to experimental warming

The effects of climate change on tropical forests may have global consequences due to the forests’ high biodiversity and major role in the global carbon cycle. In this study, we document the effects of experimental warming on the abundance and composition of a tropical forest floor herbaceous plant community in the Luquillo Experimental Forest, Puerto Rico. This study was conducted within Tropical Responses to Altered Climate Experiment (TRACE) plots, which use infrared heaters under free‐air, open‐field conditions, to warm understory vegetation and soils + 4°C above nearby control plots. Hurricanes Irma and María damaged the heating infrastructure in the second year of warming, therefore, the study included one pretreatment year, one year of warming, and one year of hurricane response with no warming. We measured percent leaf cover of individual herbaceous species, fern population dynamics, and species richness and diversity within three warmed and three control plots. Results showed that one year of experimental warming did not significantly affect the cover of individual herbaceous species, fern population dynamics, species richness, or species diversity. In contrast, herbaceous cover increased from 20% to 70%, bare ground decreased from 70% to 6%, and species composition shifted pre to posthurricane. The negligible effects of warming may have been due to the short duration of the warming treatment or an understory that is somewhat resistant to higher temperatures. Our results suggest that climate extremes that are predicted to increase with climate change, such as hurricanes and droughts, may cause more abrupt changes in tropical forest understories than longer‐term sustained warming.     

Water loss, cutaneous resistance, and effects of dehydration on locomotion of Eleutherodactylus frogs

Water loss, cutaneous resistance, and the effects of dehydration on jumping ability were measured in two neotropical frogs, the common coquí (Eleutherodactylus coqui) and the cave coquí (Eleutherodactylus cooki). In both species jumping performance declined with an increase in water loss and a greater duration of exposure to dehydrating conditions. The arboreal species, E. coqui, had a slightly higher rate of water loss and lower cutaneous resistance than the non-arboreal species, E. cooki. However, differences in cutaneous resistance and water loss were too small to explain differences in geographic distributions of these species. In both species, a decline in boundary layer resistance contributed to an increased rate of water loss at higher temperature. Accepted: 4 January 1999     

Development of six microsatellite loci for black mangrove (Avicennia germinans)

We developed six new microsatellite loci for the black mangrove (Avicennia germinans), an important member of wetland communities worldwide. Loci showed moderate to high polymorphism and a survey of four locations [Puerto Rico (Jobos Bay and Luquillo), Mexico, French Guyana] revealed clear regional (and local) population structure. All populations were genetically distinct and the two continental populations showed much higher diversity than the two insular Puerto Rican locations. These loci complement those recently published by Nettel et al. (2005 ) and promise to be valuable for characterizing local and regional population dynamics in the black mangrove.     

Conservation status assessment of the Sharp‐shinned Hawk,an endangered insular raptor in Puerto Rico

Sharp‐shinned Hawks (Accipiter striatus) are forest raptors that are widely distributed in the Americas. A subspecies endemic to Puerto Rico (A. s. venator) is listed as endangered and restricted to mature and old secondary montane forests and shade coffee plantations. However, recent information about the population status and distribution of Puerto Rican Sharp‐shinned Hawks is lacking. We developed a spatial geographic distribution model for Sharp‐shinned Hawks in Puerto Rico from 33 locations collected during four breeding seasons (2013–2016) using biologically relevant landscape variables (aspect, canopy closure, elevation, rainfall, slope, and terrain roughness). Elevation accounted for 89.8% of the model fit and predicted that the greatest probability of occurrence of Sharp‐shinned Hawks in Puerto Rico (> 60%) was at elevations above 900 m. Based on our model, an estimated 56.1 km² of habitat exists in Puerto Rico with a high probability of occurrence. This total represents ~0.6% of the island's area. Public lands included 43.8% of habitat with high probability of occurrence (24.6 km²), 96% of which was located within four protected areas. Our results suggest that Sharp‐shinned Hawks are rare in Puerto Rico and restricted to the higher elevations of the Cordillera Central. Additional research is needed to identify and address ecological limiting factors, and recovery actions are needed to avoid the extinction of this endemic island raptor.     

The Systematics and Reproductive Biology of the Galeus arae Subspecific Complex (Chondrichthyes: Scyliorhinidae)

Galeus arae is currently classified as a complex of three subspecies (Galeus arae arae, Galeus arae antillensis, and Galeus arae cadenati). Morphometric and meristic analyses, size at maturity, and variation in color patterns, support the recognition of these taxa as distinct species. All species have well-developed nidamental glands and are oviparous. Galeus arae comprises two geographically disjunct populations that are not distinguishable by the characters we examined. A northern population occurs along the east and Gulf coasts of North America from South Carolina to the Mississippi delta, and the northern coast of Cuba to the north-eastern tip of the Yucatan. A southern population occurs along the Caribbean coasts of Honduras, Nicaragua, and Costa Rica, and some neighboring islands. Galeus antillensis occurs on the northern coasts of Hispaniola and Puerto Rico, and off many of the Leeward Islands. Galeus cadenati occurs off the Caribbean coasts of Panama and Colombia. Distributional data suggest that the three species are distributed allopatrically.     

A new species of Lepanthes (Orchidaceae) from Puerto Rico

A new species,Lepanthes caritensis, is described and illustrated. There are now nine species ofLepanthes known to occur in Puerto Rico. Plant habitat and floral morphology ofL. caritensis is most similar to that ofL. sanguinea. A survey of the area where the new species is located suggests that it is rare and should be protected under the Federal Endangered Species Act. Una especic nueva,Lepanthes caritensis, es descrita e ilustrada para Puerto Rico. Con ésta hay ahora nueve especies deLepanthes en Puerto Rico. El hábito de la planta y la morfología de la flor deL. caritensis es más similar aL. sanguinea. Un muestreo del área donde se encuentra la nueva especie sugiere que ésta es rara y que debería ser protegida por el Federal Endangered Species Act.     

A seasonal population matrix model of the Caribbean Red‐tailed Hawk Buteo jamaicensis jamaicensis in eastern Puerto Rico

Reliable estimates of life history parameters and their functional role in animal population trajectories are critical, yet often missing, components in conservation and management. We developed seasonal matrix population models of the Red‐tailed Hawk Buteo jamaicensis jamaicensis in the upper and lower forests of the Luquillo Mountains, Puerto Rico, to describe the influence of early life stages (nestling and clutch survival) on population growth. Modelled populations exhibited positive discrete rates of growth in forests above 400 m (λ highlands = 1.05) and in forests below 400 m (λ lowlands = 1.27) of the Luquillo Mountains. Further, adult survival was the parameter with the highest proportional effect and direct contribution to growth of the population. Besides survival of adults, our results identified that nestling survival had the second greatest influence on λ, stressing the importance of this life stage for the population growth rate of Red‐tailed Hawks in our study area. Seasonal matrices are not commonly used to describe population dynamics of birds. However, these may be a useful tool to analyse the influence of life stages in the annual cycle to better address conservation and management needs, especially for species inhabiting oceanic islands.     

Effects of fern thickets on woodland development on landslides in Puerto Rico

Abstract. Thicket-forming ferns are common colonizers of disturbed habitats in the tropics, but little is known about their ecology. The effects of thickets formed by the fern Dicranopteris pectinata on tree seedlings on five landslides in the Luquillo Experimental Forest in northeastern Puerto Rico were both positive and negative. Soil moisture and total soil N were higher under fern thickets than in adjacent open areas and soil bulk density and soil surface temperatures were lower. Germination of seeds of the tree Cecropia schreberiana was higher for seeds sown under fern thickets than for those sown into adjacent open areas. Tree seedlings of Tabebuia hetero-phylla exhibited a threefold reduction in photosynthesis under ferns, probably resulting from a twelvefold reduction of photosynthetic photon flux density. Growth of Tabebuia seedlings was reduced under ferns but the distribution of seedlings of naturally occurring woody plants was not strongly correlated with the presence of fern thickets. Although fern thickets on low-nutrient landslide soils appear to facilitate germination, they inhibit growth of tree seedlings and may, therefore, delay forest development on landslides in Puerto Rico.     

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.     

Folivory by a tropical tanager: species of plants used and the relationship between leaf consumption and fruit abundance

ABSTRACT Folivory, or eating leaves, is unusual for small passerines. Puerto Rican Spindalises (Spindalis portoricensis, Thraupidae), tanagers endemic to the island of Puerto Rico, are known to feed on leaves, but little is known about the possible importance of leaves in their diet. Our objectives were to determine the different species of leaves eaten, the percentage of their diet consisting of leaves, and the relationship between leaf consumption and fruit abundance. We used data from previous studies where the foraging activity of Puerto Rican Spindalises was systematically sampled, and from additional observations made throughout the island. We documented 160 records of folivory, with spindalises feeding on 44 plant species in 25 plant families, including monocots, dicots, gymnosperms, and pteridophytes. Spindalises fed on young leaves of 26 plant species, and mature leaves of 19 plant species. Spindalises were primarly frugivorous (83.9% of diet), but leaves were the second most frequent food item in their diets (8.9% of diet). We also found that leaf consumption was negatively correlated with the abundance of ripe fruit, suggesting that leaves were particularly important food items when less fruit was available. The frequency of folivory by spindalises in our study was less than reported for other folivorous passerines such as plantcutters (Phytotoma spp.) and saltators (Saltator spp.). Nonetheless, folivory may help spindalises cope with human‐dominated landscapes and other environmental changes on small islands.     

Land‐use History Affects the Distribution of the Saprophytic Orchid Wullschlaegelia calcarata in Puerto Rico's Tabonuco Forest1

Human activities such as logging and agriculture can severely damage forest ecosystems by changing forest structure, ecosystem function, and biodiversity. These changes may have long‐lasting consequences, which influence forest recovery. We investigated the effect of past human disturbance on the current distribution of an understory, achlorophyllous orchid, Wullschlaegelia calcarata in Puerto Rico's tropical rain forest after 70 yr of recovery. Our study site was the 16‐ha Luquillo Forest Dynamics Plot located in the Luquillo Experimental Forest, which has four areas with differing intensity of land use that have been distinguished from variation in canopy cover seen in aerial photographs taken in 1936. We recorded orchids in six 10‐m‐wide, 500‐m‐long transects across four different areas of land‐use history. We found that the orchid was not present in an area of the plot which had <20 percent canopy cover in 1936, and was most abundant in the area with >80 percent canopy cover, which had been minimally impacted by human activity. Tree species composition varied among land‐use history areas, and our observations suggested that this variation might be influencing the local distribution of W. calcarata. We also measured leaf litter biomass and identified the leaves of litter in areas with and without the orchid. Litter with a high proportion of Buchenavia tetraphylla leaves had more orchids. Even though human disturbance ceased in 1932, land‐use history in the Luquillo Forest still casts a shadow over the distribution of W. calcarata.     

Colonization history and population differentiation of the Honey Bees (Apis mellifera L.) in Puerto Rico

Honey bees (Apis mellifera L.) are the primary commercial pollinators across the world. The subspecies A. m. scutellata originated in Africa and was introduced to the Americas in 1956. For the last 60 years, it hybridized successfully with European subspecies, previous residents in the area. The result of this hybridization was called Africanized honey bee (AHB). AHB has spread since then, arriving to Puerto Rico (PR) in 1994. The honey bee population on the island acquired a mosaic of features from AHB or the European honey bee (EHB). AHB in Puerto Rico shows a major distinctive characteristic, docile behavior, and is called gentle Africanized honey bees (gAHB). We used 917 SNPs to examine the population structure, genetic differentiation, origin, and history of range expansion and colonization of gAHB in PR. We compared gAHB to populations that span the current distribution of A. mellifera worldwide. The gAHB population is shown to be a single population that differs genetically from the examined populations of AHB. Texas and PR groups are the closest genetically. Our results support the hypothesis that the Texas AHB population is the source of gAHB in Puerto Rico.