Biology subjects

Gray, D. A.

Publications and source records attributed to Gray, D. A..

2 recordsLinked to original sources

bioRxiv2019

Molecular biogeography and host relations of a parasitoid fly

Successful geographic range expansion by parasites and parasitoids may also require host range expansion. Thus the evolutionary advantages of host specialization may trade off against the ability to exploit new host species encountered in new geographic regions. Here we use molecular techniques and confirmed host records to examine biogeography, population divergence, and host flexibility of the parasitoid fly, Ormia ochracea (Bigot). Gravid females of this fly find their cricket hosts acoustically by eavesdropping on male cricket calling songs; these songs vary greatly among the known host species of crickets. Using both nuclear and mitochondrial genetic markers, we (1) describe the geographical distribution and sub-division of genetic variation in O. ochracea from across the continental United States, the Mexican states of Sonora and Oaxaca, and populations introduced to Hawaii; (2) demonstrate that the distribution of genetic variation among fly populations is consistent with a single widespread species with regional host specialization, rather than locally differentiated cryptic species, (3) identify the more-probable source populations for the flies introduced to the Hawaiian islands; (4) examine genetic variation and sub-structure within Hawaii; and (5) discuss specialization and lability in host-finding behavior in light of the diversity of cricket songs serving as host cues in different geographically separate populations.

evolutionary biology↗

bioRxiv2019

A single dose of dietary nitrate increases maximal muscle speed and power in healthy older men and women

BackgroundAging results in reductions in maximal muscular strength, speed, and power, which often lead to functional limitations highly predictive of disability, institutionalization, and mortality in the elderly. This may be partially due to reduced nitric oxide (NO) bioavailability. We therefore hypothesized that dietary nitrate (NO3-), a source of NO via the NO3- [->] nitrite (NO2-) [->] NO enterosalivary pathway, could increase muscle contractile function in older subjects. MethodsTwelve healthy older (age 71{+/-}1 y) subjects were studied using a randomized, doubleblind, placebo-controlled, crossover design. After fasting overnight, subjects were tested 2 h after ingesting beetroot juice containing or devoid of 13.4{+/-}0.5 mmol NO3-. Plasma NO3- and NO2- and breath NO were measured periodically, and muscle function was determined using isokinetic dynamometry. ResultsNO3- ingestion increased (P<0.001) plasma NO3-, plasma NO2-, and breath NO by 1050%, 140%, and 110%, respectively. Maximal velocity of knee extension increased (P<0.01) by 1.1{+/-}0.3 rad/s, or by 10.9{+/-}3.5%. Maximal knee extensor power increased (P<0.05) by 0.14{+/-}0.06 W/kg, or by 4.4{+/-}2.3%. ConclusionsAcute dietary NO3- intake improves muscle contractility in older individuals. These findings have important implications for this population, in whom diminished muscle function can lead to functional limitations, dependence, and even premature death.

physiology↗