Showing posts with label Neotropics. Show all posts
Showing posts with label Neotropics. Show all posts

Saturday, January 28, 2012

Endemic Species, Biodiversity Hot Spots & Overlooked and Underestimated Species Diversity

Three undescribed species 
of Plica, with locations and
number of scale rows at 
midbody. Many undescribed
species of reptiles and amphibians
remain to be discovered
Conservation International reports that biodiversity hotspots hold high numbers of endemic species, but their combined area of remaining habitat cover only 2.3% of the Earth's land surface. Each hotspot is considered threatened and has lost at least 70 percent of its original natural vegetation. Over 50 percent of the world’s plant species and 42 percent of all terrestrial vertebrate species are endemic to the 34 biodiversity hotspots.

In a forthcoming paper, Swenson et al. (2012) report the Andes-Amazon basin of Peru and Bolivia as one of the most data-poor, and biologically rich areas of the world. While conservationists and scientists agree the region has extremely high endemism, perhaps the highest in the world, little was known about the geographic distributions of these species and ecosystems within country boundaries. Swenson et al. developed conservation data on endemic biodiversity (~800 species of birds, mammals, amphibians, and plants) and terrestrial ecological systems (~90; groups of vegetation communities resulting from the action of ecological processes, substrates, and/or environmental gradients) to conduct a fine scale conservation prioritization across the Amazon watershed of Peru and Bolivia. The authors modeled the geographic distributions of 435 endemic plants and all 347 endemic vertebrate species, from existing museum and herbaria specimens at a regional conservation practitioner’s scale (1:250,000- 1:1,000,000), based on the best available tools and geographic data. They mapped ecological systems, endemic species concentrations, and irreplaceable areas with respect to national level protected areas.  They found that sizes of endemic species distributions ranged widely, from a minimum of about 20  km2 to more than 200,000  km2 across the study area. Endemic bird and mammal species richness was greatest within a narrow 2500-3000 m elevation band along the length of the Andes Mountains. Endemic amphibian richness was highest at 1000-1500 m elevation and concentrated in the southern half of the study area. Of interest, amphibians displayed peaks of endemism (21-29 species per 1-km2 cell) on lower slopes, between 1000 and 1500 m elevation. These areas were concentrated in southern Peru, northern Bolivia, and in an isolated endemic area in the northern Peruvian department of San Martin. In the study region they found 177 endemic species of amphibians in 30 genera. Given that the region is poorly known many species undoubtedly remain to be found and the challenges involved in conserving the biodiversity of this region are considerable.

Thee more undescribed
species of Plica. The
top photo, may be the real, 
Plica plica
While the authors looked at most of the major groups of terrestrial vertebrates, for some unknown and unstated reason they left out reptiles. For the past few months I have been looking at some widespread neotropical reptiles and am finding a considerable amount of cryptic diversity that has been overlooked and ignored. An excellent example is the widespread lizard, Plica plica. Some times called the tree runner, these arboreal lizards sit on tree trunks and lap up ants as they march passed. While there are currently three recognized species in the genus (P. umbra, P. plica, and P. luminaria), Plica plica appears to be a superspecies. The most recent discussion of this species is probably Avila-Pires' (1997) account where she reports  Plica plica has 121-162 scales around the middle of the body and 74-95 ventrals. The list of specimens she examined included material from Guyana, Peru, Suriname, as well as Brazil.

To date I have looked at more than 60 specimens from about 25 localities ranging from Trinidad and Venezuela to Ecuador and southern Peru. My range for scales around midbody is 97 to 202, with a ventral range of 48 to 96. Conservatively, these specimens represent at least 12 species, but probably 14 or 15 species. This is of concern because species like Plica plica are often considered species of least concern,due to their perceived widespread distribution. So, yes biodiversity hot spots are of interest but it appears that much of the rest of the world is also harboring undetected, cryptic biodiversity also.

Literature
Avila-Pires, TCS, 1997. Lizards of Brazilian Amazonia (Reptilia: Squamata). Zoologische Verhandelingen 299:1-706.

Swenson JJ, Young BE, Beck S, Comer P, Cordova JH, Dyson J, Embert D, Encarnacion F, Ferreira W, Franke I, Grossman D, Hernandez P, Herzog SK, Josse C, Navarro G, Pacheco V, Stein BA, Timana M, Tovar A, Tovar C, Vargas J, Zambrana-Torrelio CM 2012. Plant and animal endemism in the eastern Andean slope: Challenges to conservation. BMC Ecology 2012, 12:1 (27 January 2012).

Sunday, May 1, 2011

Why are there so many species of Terrarana frogs?

Pristimantis urichi, a Terrarana Frog. JCM

Some evolutionary lineages have been much more successful at producing more individual species than others. Lizards of the genus Anolis and snakes in the genus Atractus have been particularly sucessful at producing large numbers of species. Gonzalez-Voyer and colleagues have used a comparative anayslis  to examine correlates of species richness for the largest radiation of Neotropical frogs, the direct-developing frogs, the Terrarana. More than 900 species are known to compose the Terrarana clade, and they make up almost 33% ofl New World Tropical frogs and 16% of the world's described species. The authord found that time the clade had been around - its age- was not significant in explain the Terrarana clade's variation in species richness. Instead, they found ecological and morphological traits explained 65% of the variance in species richness. The traits included a more vascularized ventral skin, the ability to colonize high-altitudes, and use a variety of vegetation types. These traits had a significant correlation with species richness, while large body size was marginally correlated with species richness.Thus. high-altitudes play a role in shaping clade diversity in the Neotropics while intrinsic factors, such as skin structures and possibly body size, may ultimately determine which clades are more speciose than others.

GONZALEZ-VOYER, A., PADIAL, J. M., CASTROVIEJO-FISHER, S., DE LA RIVA, I. and VILĂ€, C. (2011), Correlates of species richness in the largest Neotropical amphibian radiation. Journal of Evolutionary Biology, 24: 931–942. doi: 10.1111/j.1420-9101.2011.02243.x