Madhava Meegaskumbura

Scale‐dependent relationships between tree species richness and ecosystem function in forests

1. The relationship between species richness and ecosystem function, as measured by productivity or biomass, is of long-standing theoretical and practical interest in ecology. This is especially true for forests, which represent a majority of global biomass, productivity and biodiversity.

Comparative evolutionary diversity and phylogenetic structure across multiple forest dynamics plots: a mega-phylogeny approach

Forest dynamics plots, which now span longitudes, latitudes, and habitat types across the globe, offer unparalleled insights into the ecological and evolutionary processes that determine how species are assembled into communities. Understanding phylogenetic relationships among species in a community has become an important component of assessing assembly processes. However, the application of evolutionary information to questions in community ecology has been limited in large part by the lack of accurate estimates of phylogenetic relationships among individual species found within communities, and is particularly limiting in comparisons between communities. Therefore, streamlining and maximizing the information content of these community phylogenies is a priority. To test the viability and advantage of a multi-community phylogeny, we constructed a multi-plot mega-phylogeny of 1347 species of trees across 15 forest dynamics plots in the ForestGEO network using DNA barcode sequence data (rbcL, matK, and psbA-trnH) and compared community phylogenies for each individual plot with respect to support for topology and branch lengths, which affect evolutionary inference of community processes. The levels of taxonomic differentiation across the phylogeny were examined by quantifying the frequency of resolved nodes throughout. In addition, three phylogenetic distance (PD) metrics that are commonly used to infer assembly processes were estimated for each plot [PD, Mean Phylogenetic Distance (MPD), and Mean Nearest Taxon Distance (MNTD)]. Lastly, we examine the partitioning of phylogenetic diversity among community plots through quantification of inter-community MPD and MNTD. Overall, evolutionary relationships were highly resolved across the DNA barcode-based mega-phylogeny, and phylogenetic resolution for each community plot was improved when estimated within the context of the mega-phylogeny. Likewise, when compared with phylogenies for individual plots, estimates of phylogenetic diversity in the mega-phylogeny were more consistent, thereby removing a potential source of bias at the plot-level, and demonstrating the value of assessing phylogenetic relationships simultaneously within a mega-phylogeny. An unexpected result of the comparisons among plots based on the mega-phylogeny was that the communities in the ForestGEO plots in general appear to be assemblages of more closely related species than expected by chance, and that differentiation among communities is very low, suggesting deep floristic connections among communities and new avenues for future analyses in community ecology.

Patterns of reproductive-mode evolution in Old World tree frogs (Anura, Rhacophoridae)

The Old World tree frogs (Anura: Rhacophoridae), with 387 species, display a remarkable diversity of reproductive modes – aquatic breeding, terrestrial gel nesting, terrestrial foam nesting and terrestrial direct development. The evolution of these modes has until now remained poorly studied in the context of recent phylogenies for the clade. Here, we use newly obtained DNA sequences from three nuclear and two mitochondrial gene fragments, together with previously published sequence data, to generate a well‐resolved phylogeny from which we determine major patterns of reproductive‐mode evolution. We show that basal rhacophorids have fully aquatic eggs and larvae. Bayesian ancestral‐state reconstructions suggest that terrestrial gel‐encapsulated eggs, with early stages of larval development completed within the egg outside of water, are an intermediate stage in the evolution of terrestrial direct development and foam nesting. The ancestral forms of almost all currently recognized genera (except the fully aquatic basal forms) have a high likelihood of being terrestrial gel nesters. Direct development and foam nesting each appear to have evolved at least twice within Rhacophoridae, suggesting that reproductive modes are labile and may arise multiple times independently. Evolution from a fully aquatic reproductive mode to more terrestrial modes (direct development and foam nesting) occurs through intermediate gel nesting ancestral forms. This suggests that gel nesting is not only a possible transitional state for the evolution of terrestriality, but also that it is a versatile reproductive mode that may give rise to other terrestrial reproductive modes. Evolution of foam nesting may have enabled rhacophorids to lay a larger number of eggs in more open and drier habitats, where protection from desiccation is important. Terrestrial direct development allows frogs to lay eggs independent of bodies of water, in a diversity of humid habitats, and may represent a key innovation that facilitated the evolution of nearly half of all known rhacophorid species.

Frankixalus, a New Rhacophorid Genus of Tree Hole Breeding Frogs with Oophagous Tadpoles.

Despite renewed interest in the biogeography and evolutionary history of Old World tree frogs (Rhacophoridae), this family still includes enigmatic frogs with ambiguous phylogenetic placement. During fieldwork in four northeastern states of India, we discovered several populations of tree hole breeding frogs with oophagous tadpoles. We used molecular data, consisting of two nuclear and three mitochondrial gene fragments for all known rhacophorid genera, to investigate the phylogenetic position of these new frogs. Our analyses identify a previously overlooked, yet distinct evolutionary lineage of frogs that warrants recognition as a new genus and is here described as Frankixalus gen. nov. This genus, which contains the enigmatic ‘Polypedates’ jerdonii described by Günther in 1876, forms the sister group of a clade containing Kurixalus, Pseudophilautus, Raorchestes, Mercurana and Beddomixalus. The distinctiveness of this evolutionary lineage is also corroborated by the external morphology of adults and tadpoles, adult osteology, breeding ecology, and life history features.

A new species of Microhyla (Anura: Microhylidae) from Sri Lanka: an integrative taxonomic approach

Species boundaries of Microhyla rubra of India and Sri Lanka were assessed using the following criteria: genetic barcoding, morphology, and vocalization. We use a ca. 500 bp fragment of the 16S rRNA mitochondrial gene and show that there is an uncorrected pairwise distance of 2.7-3.2% between the Indian and Sri Lankan populations of M. rubra. We show that they are different in several call characteristics such as, dominant frequency, call duration, call rise time and pulse rate. Morphologically, the Sri Lankan population can be distinguished from the typical M. rubra described from southern India, by a combination of characters: body size, skin texture, and feet dimensions. We recognize the population from Sri Lanka as a new species, Microhyla mihintalei sp. nov., a widely distributed lowland species with an elevational distribution of up to 500 m a.s.l.

Conservation in a changing landscape: habitat occupancy of the critically endangered Tennent's leaf-nosed lizard (Ceratophora tennentii) in Sri Lanka

Landscape modification is a key driver of global species extinction. Thus, understanding how species react to changes is essential for effective conservation management in modified landscapes. We examined the impact of selected land use patterns on the critically endangered Ceratophora tennentii in the Knuckles mountain range of Sri Lanka where lizards occupy patches of both natural undisturbed forests and modified plantations – evidently, those with a forest canopy. We tested three potential explanations for non-random habitat selection: availability of suitable microhabitat pockets, availability of prey and direct threats from humans. The microhabitat pockets occupied by the lizards were characterised by shade, humidity and the density of perches. Most lizards were found in mixed cardamom forests followed by natural forests and cardamom plantations, but none were observed in the pine plantations. Food availability showed similar patterns among habitats. Direct mortality by humans did not influence the distribution of this species. Our work indicates that habitat modifications that retain the structural complexity of the vegetation would still permit the existence of the species in densities equal to or greater than that of undisturbed forest patches. It adds to a growing body of literature that signifies the importance of disturbed habitats (intermediate disturbance hypothesis) in protecting threatened species of fauna. It is highly unlikely that some disturbed habitats will be ever be returned to their former pristine state in time frames that are important for species’ conservation. Hence, attention is needed in developing suitable approaches to manage and conserve species across disturbed habitats.

Comparative Postembryonic Skeletal Ontogeny in Two Sister Lineages of Old World Tree Frogs (Rhacophoridae: Taruga, Polypedates)

Rhacophoridae, a family of morphologically cryptic frogs, with many genetically distinct evolutionary lineages, is understudied with respect to skeletal morphology, life history traits and skeletal ontogeny. Here we analyze two species each from two sister lineages, Taruga and Polypedates, and compare their postembryonic skeletal ontogeny, larval chondrocrania and adult osteology in the context of a well-resolved phylogeny. We further compare these ontogenetic traits with the direct-developing Pseudophilautus silus. For each species, we differentially stained a nearly complete developmental series of tadpoles from early postembryonic stages through metamorphosis to determine the intraspecific and interspecific differences of cranial and postcranial bones. Chondrocrania of the four species differ in 1) size; 2) presence/absence of anterolateral and posterior process; and 3) shape of the suprarostral cartilages. Interspecific variation of ossification sequences is limited during early stages, but conspicuous during later development. Early cranial ossification is typical of other anuran larvae, where the frontoparietal, exoccipital and parasphenoid ossify first. The ossification sequences of the cranial bones vary considerably within the four species. Both species of Taruga show a faster cranial ossification rate than Polypedates. Seven cranial bones form when larvae near metamorphic climax. Ossification of all 18 cranial bones is initiated by larval Gosner stage 46 in T. eques. However, some cranial bone formation is not initiated until after metamorphosis in the other three species. Postcranial sequence does not vary significantly. The comparison of adult osteology highlights two characters, which have not been previously recorded: presence/absence of the parieto-squamosal plates and bifurcated base of the omosternum. This study will provide a starting point for comparative analyses of rhacophorid skeletal ontogeny and facilitate the study of the evolution of ontogenetic repatterning associated with the life history variation in the family.

An Acoustic Analysis of the Genus Microhyla (Anura: Microhylidae) of Sri Lanka

Vocalizing behavior of frogs and toads, once quantified, is useful for systematics, rapid species identification, behavioral experimentation and conservation monitoring. But yet, for many lineages vocalizations remain unknown or poorly quantified, especially in diversity rich tropical regions. Here we provide a quantitative acoustical analysis for all four Sri Lankan congeners of the genus Microhyla. Three of these species are endemic to the island, but Microhyla ornata is regionally widespread. Two of these endemics, M. karunaratnei (Critically Endangered) and M. zeylanica (Endangered), are highly threatened montane isolates; the other, M. mihintalei, is relatively common across the dry lowlands. We recorded and analyzed 100 advertisement calls from five calling males for each species, except for M. zeylanica, which only had 53 calls from three males suitable for analyses. All four species call in choruses and their vocal repertoires are simple compared to most frogs. Their calls contain multiple pulses and no frequency modulation. We quantified eight call characters. Call duration and number of pulses were higher for the two montane isolates (inhabiting cooler habitats at higher altitudes) compared to their lowland congeners. Microhyla zeylanica has the longest call duration (of 1.8 ± 0.12 s) and the highest number of pulses (of 61–92 pulses). The smallest of the species, Microhyla karunaratnei (16.2–18.3 mm), has the highest mean dominant frequency (3.3 ± 0.14 kHz) and pulse rate (77 ± 5.8 pulses per second). The calls separate well in the Principal Component space: PC1 axis is mostly explained by the number of pulses per call and call duration; PC2 is mostly explained by the pulse rate. A canonical means plot of a Discriminant Function analysis shows non-overlapping 95% confidence ellipses. This suggests that some call parameters can be used to distinguish these species effectively. We provide detailed descriptions for eight call properties and compare these with congeners for which data is available. This work provides a foundation for comparative bioacoustic analyses and species monitoring while facilitating the systematics of Microhyla across its range.

From Clinging to Digging: The Postembryonic Skeletal Ontogeny of the Indian Purple Frog, Nasikabatrachus sahyadrensis (Anura: Nasikabatrachidae)

The Indian Purple frog, Nasikabatrachus sahyadrensis, occupies a basal phylogenetic position among neobatrachian anurans and has a very unusual life history. Tadpoles have a large ventral oral sucker, which they use to cling to rocks in torrents, whereas metamorphs possess adaptations for life underground. The developmental changes that underlie these shifts in habits and habitats, and especially the internal remodeling of the cranial and postcranial skeleton, are unknown. Using a nearly complete metamorphic series from free-living larva to metamorph, we describe the postembryonic skeletal ontogeny of this ancient and unique monotypic lineage. The torrent-dwelling larva possesses a dorsoventrally flattened body and a head with tiny dorsal eyes, robust lower and upper jaw cartilages, well-developed trabecular horns, and a definable gap between the trabecular horns and the tip of the snout. Unlike tadpoles of many other frogs, those of Nasikabatrachus retain larval mouthparts into late metamorphic stages. This unusual feature enables the larvae to maintain their clinging habit until near the end of metamorphosis. The subsequent ontogenetic shift from clinging to digging is correlated with rapid morphological changes and behavioral modifications. Metamorphs are equipped with a shortened tibiafibula and ossified prehallical elements, which likely facilitate initial digging using the hind limbs. Subsequently, the frogs may shift to headfirst burrowing by using the wedge-shaped skull, anteriorly positioned pectoral girdle, well-developed humeral crests and spatula-shaped forelimbs. The transition from an aquatic life in torrents to a terrestrial life underground entails dramatic changes in skeletal morphology and function that represent an extreme in metamorphic remodeling. Our analysis enhances the scope for detailed comparative studies across anurans, a group renowned for the diversity of its life history strategies.

Life among crevices: osteology of Nannophrys marmorata (Anura: Dicroglossidae).

Nannophrys Gunther, 1868, a group of flat-bodied frogs, is an endemic Sri Lankan genus bearing three extant and one extinct species, adapted to live among narrow and horizontal rock crevices adjacent to clear water streams. One of these species, Nannoprhys marmorata Kirtisinghe, 1946 is mostly restricted to the rock strewn streams of the Knuckles region (200–1200 m asl). Here, we re-describe the osteology of Nannophrys marmorata highlighting apomorphies and adaptations for life between narrow spaces . Previous studies on skeletal morphology of the genus Nannophrys include Gunther (1869), Boulenger (1882, 1890), Noble (1931), Kirtisinghe (1946), Clarke (1983) and Scott (2005). Basic descriptions of the skeleton of N. marmorata have been done (Kirtisinghe 1946; Clarke 1983), on which we build and elaborate. We describe the osteology using three adult specimens (SVL= 35.2–36.5 mm) of N. marmorata , stained differentially for bone and cartilage following the procedure by Taylor and Van Dyke (1985); we follow the osteological terminology of Trueb (1973), Duellman and Trueb (1986), and Pugener and Maglia (1997, 2009).