Abstract A steady supply of hosts at the susceptible stage for parasitism is a major component of mass rearing parasitoids for biological control programs. Here we describe the effects of storing 5th instar Plodia interpunctella larvae in dormancy on subsequent host development in the context of host colony maintenance and effects of the duration of host dormancy on the development of Habrobracon hebetor parasitoids reared from dormant hosts. We induced dormancy with a combination of short daylength (12L:12D) and lower temperature (15°C), conditions known to induce diapause in this species, and held 5th instar larvae of P. interpunctella for a series of dormancy durations ranging from 15 to 105 days. Extended storage of dormant 5th instar larvae had no significant impacts on survival, development, or reproductive potential of P. interpunctella , reinforcing that dormant hosts have a substantial shelf life. This ability to store hosts in dormancy for more than 3 months at a time without strong negative consequences reinforces the promise of using dormancy to maintain host colonies. The proportion of hosts parasitized by H. hebetor did not vary significantly between non-dormant host larvae and dormant host larvae stored for periods as long as 105 days. Concordant with a prior study, H. hebetor adult progeny production from dormant host larvae was higher than the number of progeny produced on non-dormant host larvae. There were no differences in size, sex ratio, or reproductive output of parasitoids reared on dormant hosts compared to non-dormant hosts stored for up to 105 days. Larval development times of H. hebetor were however longer when reared on dormant hosts compared to non-dormant hosts. Our results agree with other studies showing using dormant hosts can improve parasitoid mass rearing, and we show benefits for parasitoid rearing even after 3 months of host dormancy.
more »
« less
The target of selection matters: An established resistance—development‐time negative genetic trade‐off is not found when selecting on development time
Trade‐offs are fundamental to evolutionary outcomes and play a central role in eco‐evolutionary theory. They are often examined by experimentally selecting on one life‐history trait and looking for negative correlations in other traits. For example, populations of the moth
- NSF-PAR ID:
- 10457078
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Journal of Evolutionary Biology
- Volume:
- 33
- Issue:
- 8
- ISSN:
- 1010-061X
- Format(s):
- Medium: X Size: p. 1109-1119
- Size(s):
- ["p. 1109-1119"]
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
more » « less
Abstract Life history theory provides a framework for understanding how trade-offs generate negative trait associations. Among nestling birds, time spent in the nest, risk of predation, and lifespan covary, but some associations are only found within species while others are only observed between species. A recent comparative study suggests that allocation trade-offs may be alleviated by disinvestment in ephemeral traits, such as nest-grown feathers, that are quickly replaced. However, direct resource allocation trade-offs cannot be inferred from interspecific trait associations without complementary intraspecific studies. Here, we asked whether there is evidence for a within-species allocation trade-off between feather quality and time spent in the nest in Tree Swallows (Tachycineta bicolor). Consistent with the idea that ephemeral traits are deprioritized, nest-grown feathers had lower barb density than adult feathers. However, despite substantial variation in fledging age among nestlings, there was no evidence for a negative association between time in the nest and feather quality. Furthermore, accounting for differences in resource availability by considering provisioning rate and a nest predation treatment did not reveal a trade-off that was masked by variation in resources. Our results are most consistent with the idea that the interspecific association between development and feather quality arises from adaptive specialization, rather than from a direct allocation trade-off.
-
more » « less
Abstract Accurately predicting responses to selection is a major goal in biology and important for successful crop breeding in changing environments. However, evolutionary responses to selection can be constrained by such factors as genetic and cross‐environment correlations, linkage, and pleiotropy, and our understanding of the extent and impact of such constraints is still developing. Here, we conducted a field experiment to investigate potential constraints to selection for drought resistance in rice (
Oryza sativa ) using phenotypic selection analysis and quantitative genetics. We found that traits related to drought response were heritable, and some were under selection, including selection for earlier flowering, which could allow drought escape. However, patterns of selection generally were not opposite under wet and dry conditions, and we did not find individual or closely linked genes that influenced multiple traits, indicating a lack of evidence that antagonistic pleiotropy, linkage, or cross‐environment correlations would constrain selection for drought resistance. In most cases, genetic correlations had little influence on responses to selection, with direct and indirect selection largely congruent. The exception to this was seed mass under drought, which was predicted to evolve in the opposite direction of direct selection due to correlations. Because of this indirect effect on selection on seed mass, selection for drought resistance was not accompanied by a decrease in seed mass, and yield increased with fecundity. Furthermore, breeding lines with high fitness and yield under drought also had high fitness and yield under wet conditions, indicating that there was no evidence for a yield penalty on drought resistance. We found multiple genes in which expression influenced both water use efficiency (WUE) and days to first flowering, supporting a genetic basis for the trade‐off between drought escape and avoidance strategies. Together, these results can provide helpful guidance for understanding and managing evolutionary constraints and breeding stress‐resistant crops. -
more » « less
Summary Small herbivores face risks of predation while foraging and are often forced to trade off food quality for safety. Life history, behaviour, and habitat of predator and prey can influence these trade‐offs. We compared how two sympatric rabbits (pygmy rabbit,
B rachylagus idahoensisS ylvilagus nuttalliiN orthA merica respond to amount and orientation of concealment cover and proximity to burrow refuges when selecting food patches. We predicted that both rabbit species would prefer food patches that offered greater concealment and food patches that were closer to burrow refuges. However, because pygmy rabbits are small, obligate burrowers that are restricted to sagebrush habitats, we predicted that they would show stronger preferences for greater cover, orientation of concealment, and patches closer to burrow refuges. We offered two food patches to individuals of each species during three experiments that either varied in the amount of concealment cover, orientation of concealment cover, or distance from a burrow refuge. Both species preferred food patches that offered greater concealment, but pygmy rabbits generally preferred terrestrial and mountain cottontails preferred aerial concealment. Only pygmy rabbits preferred food patches closer to their burrow refuge. Different responses to concealment and proximity to burrow refuges by the two species likely reflect differences in perceived predation risks. Because terrestrial predators are able to dig for prey in burrows, animals like pygmy rabbits that rely on burrow refuges might select food patches based more on terrestrial concealment. In contrast, larger habitat generalists that do not rely on burrow refuges, like mountain cottontails, might trade off terrestrial concealment for visibility to detect approaching terrestrial predators. This study suggests that body size and evolutionary adaptations for using habitat, even in closely related species, might influence anti‐predator behaviors in prey species. -
more » « less
Abstract The strategies by which animals allocate reproductive effort across their lifetimes vary, and the causes of variation in those strategies are actively debated. In birds, most research has focused heavily on variation in clutch size and fecundity, but incubation behaviour and other functionally related traits have received less attention. Variation in incubation period duration is notable because time‐dependent sources of clutch mortality should impose strong directional selection to minimize the incubation period. However, life‐history theory predicts multiple mechanisms by which inter‐ and intraspecific variation in incubation behaviours may be adaptive.
We conducted one of the first studies of intraspecific latitudinal variation in avian incubation behaviours across a large portion of a single species’ range. We placed motion‐activated nest cameras inside burrowing owl nests at five study sites to quantify variation in daily nest attentiveness, cumulative nest attendance and incubation period duration. We tested predictions of two alterative hypotheses that have been proposed to explain variation in incubation periods: the
parental risk tolerance hypothesis and theneonate quality hypothesis .Daily nest attentiveness, cumulative nest attendance and incubation period duration in burrowing owls were all positively correlated with latitude. Burrowing owls reduced their daily nest attentiveness at low latitudes and on days when the average nest temperature was within the range that is optimal for embryo development. Further, longer incubation periods were most strongly associated with greater cumulative nest attendance instead of reduced daily nest attentiveness.
These results support predictions of the
neonate quality hypothesis: longer incubation periods result from stronger selection on neonate quality rather than selection to reduce reproductive effort in response to low extrinsic mortality risk. However, some owls facultatively reduced their daily nest attentiveness, and this result supports the general hypothesis that incubation decisions reflect a trade‐off between reproduction and self‐maintenance, and that the optimal solution to that trade‐off varies systematically in response to latitudinal gradients in adult mortality.A free
Plain Language Summary can be found within the Supporting Information of this article.
