Narrow thermal tolerance and low dispersal drive higher speciation in tropical mountains.

Species richness is greatest in the tropics, and much of this diversity is concentrated in mountains. Janzen proposed that reduced seasonal temperature variation selects for narrower thermal tolerances and limited dispersal along tropical elevation gradients [Janzen DH (1967) Am Nat 101:233-249]. These locally adapted traits should, in turn, promote reproductive isolation and higher speciation rates in tropical mountains compared with temperate ones. Here, we show that tropical and temperate montane stream insects have diverged in thermal tolerance and dispersal capacity, two key traits that are drivers of isolation in montane populations. Tropical species in each of three insect clades have markedly narrower thermal tolerances and lower dispersal than temperate species, resulting in significantly greater population divergence, higher cryptic diversity, higher tropical speciation rates, and greater accumulation of species over time. Our study also indicates that tropical montane species, with narrower thermal tolerance and reduced dispersal ability, will be especially vulnerable to rapid climate change.

Foraging history of individual elephants using DNA metabarcoding.

Individual animals should adjust diets according to food availability. We used DNA metabarcoding to construct individual-level dietary timeseries for elephants from two family groups in Kenya varying in habitat use, social position and reproductive status. We detected at least 367 dietary plant taxa, with up to 137 unique plant sequences in one fecal sample. Results matched well-established trends: elephants tended to eat more grass when it rained and other plants when dry. Nested within these switches from 'grazing' to 'browsing' strategies, dietary DNA revealed seasonal shifts in food richness, composition and overlap between individuals. Elephants of both families converged on relatively cohesive diets in dry seasons but varied in their maintenance of cohesion during wet seasons. Dietary cohesion throughout the timeseries of the subdominant 'Artists' family was stronger and more consistently positive compared to the dominant 'Royals' family. The greater degree of individuality within the dominant family's timeseries could reflect more divergent nutritional requirements associated with calf dependency and/or priority access to preferred habitats. Whereas theory predicts that individuals should specialize on different foods under resource scarcity, our data suggest family bonds may promote cohesion and foster the emergence of diverse feeding cultures reflecting links between social behaviour and nutrition.

Plant DNA-barcode library and community phylogeny for a semi-arid East African savanna.

Applications of DNA barcoding include identifying species, inferring ecological and evolutionary relationships between species, and DNA metabarcoding. These applications require reference libraries that are not yet available for many taxa and geographic regions. We collected, identified, and vouchered plant specimens from Mpala Research Center in Laikipia, Kenya, to develop an extensive DNA-barcode library for a savanna ecosystem in equatorial East Africa. We amassed up to five DNA barcode markers (rbcL, matK, trnL-F, trnH-psbA, and ITS) for 1,781 specimens representing up to 460 species (~92% of the known flora), increasing the number of plant DNA barcode records for Africa by ~9%. We evaluated the ability of these markers, singly and in combination, to delimit species by calculating intra- and interspecific genetic distances. We further estimated a plant community phylogeny and demonstrated its utility by testing if evolutionary relatedness could predict the tendency of members of the Mpala plant community to have or lack "barcode gaps", defined as disparities between the maximum intra- and minimum interspecific genetic distances. We found barcode gaps for 72%-89% of taxa depending on the marker or markers used. With the exception of the markers rbcL and ITS, we found that evolutionary relatedness was an important predictor of barcode-gap presence or absence for all of the markers in combination and for matK, trnL-F, and trnH-psbA individually. This plant DNA barcode library and community phylogeny will be a valuable resource for future investigations.

The Banded-wing Moselia infuscata (Claassen) Phenotype from California and Oregon, U.S.A. (Plecoptera: Leuctridae).

Moselia specimens from California and Oregon with a banded-wing phenotype were found to be indistinguishable morphologically from those of M. infuscata (Claassen) with typical wing pigment pattern. Preliminary DNA barcode data (Cytochrome c Oxidase subunit I [COI]), however, show significant genetic variation among four populations including three from northern California sites and one from southern Oregon. Although this genetic variation exceeded standard divergence thresholds often used to recognize distinct stream insect species, no new taxa are proposed at this time due to the preliminary nature of the data. 

Discovery of new populations and DNA barcoding of the Arapahoe snowfly Arsapnia arapahoe (Plecoptera: Capniidae).

The Arapahoe Snowfly, Arsapnia arapahoe (Nelson & Kondratieff)was recently discovered in six different first-order streams outside of the Cache la Poudre River Basin where it was previously considered endemic. Specimens of A. arapahoe were always collected in much lower relative abundance, 1.09% (±2.3SD), than other sympatric adult capniids. The first mitochondrial deoxyribonucleic acid (DNA) barcodes for A. arapahoe and A. coyote (Nelson & Baumann) are presented and compared with those of A. decepta. DNA barcoding was not able to differentiate between A. arapahoe and A. decepta Banks but it was able to indicate that A. coyote is specifically distinct.