Showing posts with label cryptic species. Show all posts
Showing posts with label cryptic species. 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.

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).

Friday, December 30, 2011

Cryptic Frogs Locate Their Respective Mates by Calls

A member of the Hyla versicolor Complex. JCM

Columbia, MO – When it comes to love songs, female tree frogs are pretty picky. According to a new study from the University of Missouri, certain female tree frogs may be remarkably attuned to the songs of mates who share the same number of chromosomes as they do. The discovery offers insight into how new frog species may have evolved.

Carl Gerhardt, Curators Professor of Biological Sciences in the MU College of Arts and Science and doctoral student Mitch Tucker studied two closely related species of grey tree frogs that live in Missouri, the eastern grey tree frog (Hyla versicolor) and the Cope’s grey tree frog (H. chrysoscelis).

“To the naked eye – human and frog – the two frogs look exactly alike,” Gerhardt said. “The frogs differ only in the number of chromosomes. The eastern grey tree frog has double the number of chromosomes.”

To the ears of potential mates, the two species differ in their vocal performances.

“The males are both singing the same love song – just one frog is singing it slower. It’s kind of like the difference between Eric Clapton’s original and unplugged versions of Layla,” Tucker said.

In previous studies, the scientists found that tree frogs with more sets of chromosome have larger cell sizes, which slows down the trill rate. What was not known was whether the calling preferences of females are similarly linked to chromosome number.

To answer this question, Tucker simulated the chromosome duplication event by replicating spring temperatures early in the frog development. Females were grown to maturity and then exposed to computer-generated, synthetic male calls that differed by trill rate. They found that the females hopped toward the calls with the trill rate of the males with matching chromosome numbers, which indicates female preference.

“This shows that chromosome number alone can control the behavior that keeps the species separate,” Gerhardt said. “In turn, as chromosome number increases, so does the size of cells, which is probably the immediate cause of the changes in calls and preferences.”

In animals, the origin of species is often associated with geographic barriers. A large body of water or range of mountains, for example, splits a large population and prevents mating. The eastern grey tree frog, according to Gerhardt, may represent a rare case of rapid evolution occurring by chromosome duplication, changes in behavior and reproductive isolation.

The report, titled “Parallel changes in mate-attracting calls and female preferences in autotriploid tree frogs,” was published by the journal Proceedings of the Royal Society B-Biological Sciences. The study was supported by funding from the National Science Foundation, National Institutes of Health, and the University of Missouri Research Board.

Tucker, M. and C. Gerhardt. 2011. Parallel changes in mate-attracting calls and female preferences in autotriploid tree frogs. Proceedings of the Royal Society B-Biological Sciences, doi: 10.1098/rspb.2011.1968