Related Articles: "phasm"
A few previous studies of marine organisms, although including a small number of independent comparisons, have used dispersal ability as the predictor of Ne differences and have indeed observed differences in dN/dS ratios [14,15]. Molecular patterns have been examined for bird flight loss [16], with the expectation of reduced Ne for FL bird lineages, partially as FL birds are more often found on islands. Additionally, Shen et al. [16] expected and observed higher dN/dS ratios in FL bird energy-related genes due to a hypothesized relaxation of selective constraints on those genes following the loss of flight. Although the biology of birds and insects differ greatly (e.g. endothermy versus ectothermy), flying metabolic rate in insects is estimated at 50 times higher than resting rate [17,18], and thus we may also observe similar patterns in insects relating to relaxed constraints on energy metabolism. We would expect energy-related influences to mainly affect mitochondrial and nuclear genes involved in the oxidative phosphorylation (OXPHOS) pathway and effective population size influences to have a genome-wide effect.
Related articles: "phasm"
The strong pattern across mitochondrial genes is likely at least partially due to a relaxation of selective constraints associated with flight loss, as was observed for bird flight loss [16]. Flight is an energetically costly activity; insect flying metabolic rate is estimated at 50 times higher than that at rest [17,18]. Therefore, the loss of flight may result in decreased selection pressure to maintain efficient energy production. For example, the winged morph of a grasshopper species consumes significantly more energy than the wingless morph [48], and winged individuals of pea aphids show increased transcription levels of genes related to energy production relative to unwinged morphs [49]. Although these studies examined intraspecific differences in flight ability, energy consumption or expression differences might be expected between FL and F species as well. These expectations of differences in energy-gene constraints are not limited to flight loss itself, as patterns among mitochondrial genes are also observed for mammals that are less locomotive compared with their more highly locomotive relatives [16]. The relaxation of purifying selection in those relevant genes could allow more non-synonymous mutations to accumulate. This would be expected in both mitochondrial and nuclear genes involved with energy production. Since the OXPHOS pathway produces 95% of the ATP needed for locomotion [50,51], these genes are expected to show the strongest effects. The OXPHOS genes included in this study are the mitochondrial genes COI, COII and cytB. Shen et al. [16] did not observe a significant difference between weakly and strongly locomotive birds for COI specifically, as was found in this study of insects. Insects are ectotherms and do not have metabolic rates that are as high as endotherms such as birds [52]. Thus, it could be that insects may expend a higher proportion of their total energy budget on flight than birds, and a stronger pattern in OXPHOS genes might therefore be expected in insects relating to locomotion.
Most of the energy-linked genes that were available for this study are mitochondrial. The nuclear gene IDH is also involved in energy metabolism; it has been observed in a species of cricket that the long-winged morph had greater transcript abundance and protein concentration of the lipogenic enzyme NADP IDH than the short-winged (FL) morph [53]. However, we expect that mitochondrial and nuclear genes in this study generally represent different functional categories, and that mitochondrial genes would show the strongest patterns relating to energy. If indeed the patterns are related to energy metabolism, the results of this study do not give support to the hypothesis by Martin & Palumbi [54], where higher mutation rates are expected with increased metabolic rates. By that hypothesis, we would expect FL lineages also to have decreased dS rates compared with F lineages due to reduced metabolic rates. Although this may be true within certain groups included in the study, we did not observe such patterns in dS rates overall in our analyses.
Interestingly, there was no difference in patterns between FFL and bsFL comparisons, with mitochondrial patterns being strong in each category. Also interesting is the observation of a strong pattern in mitochondrial genes at all, given the major hypothesized cause of flight loss (specifically in females) as an energy trade-off [18,47]. If the energy saved by being FL is being used elsewhere by the organism, we might not expect the genetic energy pathways to be under less intense purifying selection. In addition, half of the cases of flight loss used in this study are transitions to female flightlessness, where relaxed purifying selection would allow deleterious mutations in OXPHOS genes to be passed onto F male offspring. Further work could examine whether the F male counterparts experience any reduction in flight ability, either due to genetic correlation of wing-related genes with females that have wing reduction, as suggested by [18], or due to sharing of those energy-relevant genes with the females.
Mark Bloch is a writer, performer, videographer and multi-media artist living in Manhattan. In 1978, this native Ohioan founded the Post(al) Art Network a.k.a. PAN. NYU's Downtown Collection now houses an archive of many of Bloch's papers including a vast collection of mail art and related ephemera. For three decades Bloch has done performance art in the USA and internationally. In addition to his work as a writer and fine artist, he has also worked as a graphic designer for ABCNews.com, The New York Times, Rolling Stone and elsewhere. He can be reached at bloch.mark@gmail.com and PO Box 1500 NYC 10009.
Pogonogaster has also been redescribed or quoted by other authors in particular GIGLIO-TOS (1927), BEIER (1935), TERRA (1995), JANTSCH (1999), EHRMANN (2002) and EHRMANN & KOCAK (2009). BEIER (1935) establishing the genus as the type of Pogonogasterini tribe (= subtribe Pogonogasterees) because of the unusual morphological features shared with other related genera within the subfamily Oligonicinae including the genera Carrikerella Hebard, 1822; Liguanea Rehn & Hebard, 1938; Mantellias Westwood, 1885; Mantillica Westwood, 1889; Pseudopogonogaster Beier, 1942 and Thesprotia Stal, 1877 (BEIER, 1935, 1964; AGUDELO et al., 2007; EHRMANN & KOCAK, 2009).
In addition to the original description of P. tristani by REHN (1918), in 1935 the same author related more detail aboutthe habitat type locality after two visits the scientist conducted in 1923 and 1927 in order to locate more specimens of this species, but without positive results. However a student (Prof. J.F. Tristan) collected another specimen some years earlier but with an unknown exact location. According to this author, La Palma is 1600 m. above sea level (5000 feet) on the pass between the western side of Irazú volcano and the Zurquí near to Barba volcano. This pass was traversed by an old road from the abandoned terminal "Linea Vieja" and Carrillo to the capital city, San José. The locality consisted of a small group of goat and cattle ranches with meadows and pastures interspersed by patches of subtropical cloudrainforest which prevails in mountainous areas of the entire passin mention. Most of the year the northeast trade windsbring moisture vaporthrough the La Palma pass. Days of sunshine duringthe wet season are exceptional, normally there is a permanent fog blanket with frequent rain or drizzle. Consequently the trees of the forest are buried in epiphytic vegetation: bromeliads, creepers, ferns and mosses covering the bark and even the fence posts and telephone wires.
The unusual shape of the body of Pogonogaster with a multilobed abdomen, the thin gnarled sides of the pronotum, and its greenish yellow color help it blend in with mosses and the epiphytes growing on the trees, as occurs with other genera of related mantids such as Pseudopogonogaster Beier, 1942; Carrikerella Hebard, 1921 and certain phasmids belonging to the genera Mirophasma (Redtenbacher, 1906), Acanthoclonia (Stal, 1875) and Laciniobethra Conle, Henneman & Gutierrez, 2014 (AYALA & ONORE, 2001; SALAZAR & CARREJO, 2002; SALAZAR, 2006; GUTIÉRREZ & BACCA, 2014; GUTIÉRREZ-VALENCIA et al., 2014). 041b061a72