Papers by Stephen Hendrix
The Journal of the Iowa Academy of Science: JIAS, 1999
Agriculture, Ecosystems & Environment, May 1, 2018
Declines in pollinators, particularly wild bees, along with rising demands for their services has... more Declines in pollinators, particularly wild bees, along with rising demands for their services has intensified efforts to examine bee communities in different types of habitats. In this study we use a phylogenetic approach to compare and contrast bee communities associated with six small produce farms, eight large prairies, and five naturally small hill prairies in Iowa. We compare the mean phylogenetic distance (MPD) and the mean nearest taxon distance (MNTD) of bees in each community to expected mean MPD and MNTD values generated from 1000 random permutations of a tree composed of 144 species found across all sites. Standardized effect size scores for MPD using presence-absence data showed significant clustering of bee communities at five of six farms and two of the five hill prairies. Clustering at the farms and hill prairies was due primarily to the significantly lower number of species in the Andrenidae (0-5 species per site), especially species of Andrena, as well as significantly greater number of species in the Halictidae (9-22 species/site), particularly Lasioglossum (Dialictus). Lack of Andrenidae spp. may be related to a lack of appropriate floral resources, indicating that enriched prairie plantings for pollinators at farms could enhance the abundance of Andrena species and hence pollinator services at these sites. The higher richness of the ground-nesting Lasioglossum likely results from soil disturbance regimes at produce farms and the naturally shallow, rocky soil with exposed surface at hill prairies, respectively. Analyses of MNTD using either abundance weighted or presence-absence data and analyses of MPD using abundance data did not indicate consistent differences between the three site types, but do point to important differences between sites in phylogenetic composition of bee communities. Our results show that phylogenetic analyses of wild bee community diversity may be a useful tool for measuring how bee communities differ in composition as a result of natural variation and human-related changes in landscapes.
The Evolutionary Ecology of Plants, 2019
Evolutionary Ecology Research, 2018
Background: Novel associations of specialist insect herbivores with host plants are frequently as... more Background: Novel associations of specialist insect herbivores with host plants are frequently assembled. If herbivore and host co-evolve following their first interactions, we would expect increases over evolutionary time in plant tolerance to attack, and usually decreases over time in insect virulence (because most insect herbivores depend for resources on continued survival of their hosts). The result should be a pattern of decreased herbivore impact through time. This is the 'evolution-of-impact hypothesis'. Organism: Two specialist gallmakers of the goldenrods Solidago altissima L. and S. gigantea Ait.: Rhopalomyia solidaginis/capitata (Diptera: Cecidomyiidae), and Eurosta solidaginis (Diptera: Tephritidae). Site of experiments: Tallgrass prairie at two sites in Iowa, USA. Predictions: For both gallmakers, S. gigantea is the novel host and S. altissima the older one. We therefore predict a higher impact of both gallmakers on S. gigantea than S. altissima. However, we predict a similar impact on each species of mechanical damage, with which both hosts have long evolutionary experience. Methods: We measured the aboveground biomass of galled and ungalled ramets from the field to assess herbivore impact by each gallmaker on each species. We used stem width-biomass relationships for ungalled ramets, applied to stem widths of galled ramets, to estimate the potential biomass of galled ramets in the absence of attack. We calculated impact as potential minus actual biomass. We also re-analysed similar data for a third gallmaker of the same hosts, Gnorimoschema gallaesolidaginis (Lepidoptera: Gelechiidae) from Heard and Kitts (2012). We assessed impacts of mechanical damage with field and greenhouse experiments of clipping and defoliation damage imposed on ramets of each species. Results: All three gallmakers had a higher impact on the novel host (S. gigantea) and, combined across all datasets, the pattern of higher impact on the novel host was highly significant. Impacts of mechanical damage did not differ between host species. Conclusions: Patterns in impacts of goldenrod gallmakers on their hosts are consistent with the evolution-of-impact hypothesis.
Dispersal ability and host‐plant characteristics influence spatial population structure of monoph... more Dispersal ability and host‐plant characteristics influence spatial population structure of monophagous beetles
Evolution, 1992
This study examined the effects of increased leaf nitrogen in natural host-plants (Plantago spp.)... more This study examined the effects of increased leaf nitrogen in natural host-plants (Plantago spp.) on female oviposition preference, larval performance, and larval chemical defense of the butterfly Junonia coenia. Increased availability of soil nutrients caused the hostplant's foliar nitrogen to increase and its chemical defense to decrease. Larval performance did not correlate with increases in foliar nitrogen. Larval growth rate and survival were equivalent across host-plant treatments. However, larvae raised on fertilized host-plants showed concomitant decreases in chemical defense as compared to larvae reared on unfertilized host-plants. Since most butterfly larvae cannot move long distances during their first few instars and are forced to feed upon the plant on which they hatched, J. coenia larval chemical defense is determined, in large part, by female oviposition choice. Female butterflies preferred host-plants with high nitrogen over host-plants with low nitrogen; however, this preference was also mediated by plant chemical defense. Female butterflies preferred more chemically defended host-plants when foliar nitrogen was equivalent between host-plants. J. coenia larvae experience intense predation in the field, especially when larvae are not chemically well defended. Any qualitative or quantitative variation in plant allelochemical defense has fitness consequences on these larvae. Thus, these results indicate that females may be making sub-optimal oviposition decisions under a nutrient-enriched regime, when predators are present. Given the recent increase in fertilizer application and nitrogen deposition on the terrestrial landscape, these interactions between female preference, larval performance, and larval chemical defense may result in long-term changes in population dynamics and persistence of specialist insects.
Using social networking services is becoming more popular day by day. The websites of the social ... more Using social networking services is becoming more popular day by day. The websites of the social networks like facebook currently are among the most popular internet services just after giant portals such as Yahoo, MSN and search engines like Google. One of the main problems in analyzing these networks is the prediction of relationships between people in the network. The purpose of this paper is to forecast the friendship of a person with a new person using existing data on Flickr website accurately. In this paper, we achieved about 90% percent correct prediction with regards to the results which are obtained by using data mining methods.
Alpine plant communities provide an exceptional system in which to test hypotheses about the dete... more Alpine plant communities provide an exceptional system in which to test hypotheses about the determinants of species diversity. Plants in this environment are exposed to extremely cold temperatures, short growing seasons, and severe soil disturbance (77). Short stature, dense prostrate growth forms, and a perennial life history are all adaptations made by plants to survive in the alpine (77). Despite this "stressful" environment, remarkable spatial patterns of species diversity are evident. Due to sharp environmental gradients, very different plant communities can be found within a few meters of one another (10, 11, 97). Also, plant diversity in alpine communities may be much higher at a fine scale (e.g. < 1 m 2) than other temperate plant communities (75). This could simply be due to greater subdivision of space owing to the small growth form of many alpine species (55, 77). Alternatively, it may be that high species diversity in alpine plants is the result of fine scale spatial heterogeneity in the environment (84, 122).
Ecology and Evolution, 2016
Ploidy elevation is increasingly recognized as a common and important source of genomic variation... more Ploidy elevation is increasingly recognized as a common and important source of genomic variation. Even so, the consequences and biological significance of polyploidy remain unclear, especially in animals. Here, our goal was to identify potential life history costs and benefits of polyploidy by conducting a large multiyear common garden experiment in Potamopyrgus antipodarum, a New Zealand freshwater snail that is a model system for the study of ploidy variation, sexual reproduction, host-parasite coevolution, and invasion ecology. Sexual diploid and asexual triploid and tetraploid P. antipodarum frequently coexist, allowing for powerful direct comparisons across ploidy levels and reproductive modes. Asexual reproduction and polyploidy are very often associated in animals, allowing us to also use these comparisons to address the maintenance of sex, itself one of the most important unresolved questions in evolutionary biology. Our study revealed that sexual diploid P. antipodarum grow and mature substantially more slowly than their asexual polyploid counterparts. We detected a strong negative correlation between the rate of growth and age at reproductive maturity, suggesting that the relatively early maturation of asexual polyploid P. antipodarum is driven by relatively rapid growth. The absence of evidence for life history differences between triploid and tetraploid asexuals indicates that ploidy elevation is unlikely to underlie the differences in trait values that we detected between sexual and asexual snails. Finally, we found that sexual P. antipodarum did not experience discernable phenotypic variance-related benefits of sex and were more likely to die before achieving reproductive maturity than the asexuals. Taken together, these results suggest that under benign conditions, polyploidy does not impose obvious life history costs in P. antipodarum and that sexual P. antipodarum persist despite substantial life history disadvantages relative to their asexual counterparts.
We examined the mating system 'of candle anemone (Anemone cylindrica) , a herbaceous prairie pere... more We examined the mating system 'of candle anemone (Anemone cylindrica) , a herbaceous prairie perennial. Four lines of evidence suggested that this species is autogamous: first, anthers shed pollen as stigmas matured, resulting in homogamy; second, only 7% of emasculated flowers received any pollen (usually one grain), and none set fruit; third, caged and open pollinated flowers had nearly 100% fFUit set; and fourth, the pollen-ovule ratio was 371 ± 54,7 (±S.D.), within the known range of autogamous species. Understanding the mating system of prairie species is important to conservation efforts because autogamous species, such as Anemone cylindrica, are more likely to survive in a fragmented landscape than xenogamous species, which are dependent on pollinator service. However, small populations of autogamous and xenogamous species are equally vulnerable to destruction by stochastic events. Thus, autogamous as well as xenogamous species will benefit by protection at the habitat level.
Small patches in fragmented habitats might fUllction as sinks, as islands suitable for colonizati... more Small patches in fragmented habitats might fUllction as sinks, as islands suitable for colonization, or they might facilitate movement of animals through the matrix from one suitable patch to another even though they might not support self-sustaining populations. Using mark-recapture procedures with the monophagous dogbane beetle (Clll)lsochus auratus), we examined the use of experimental clusters of its host plant, Indian hemp dogbane (Apocynum cannabinum), radiating out from large, natural patches. Experimental clusters of plants were placed as single clusters at varying distances up to 100 m from seven natural patches and in "stepping stone" fashion of clusters every 25 m. Based on known movement pattems in the dogbane beetle, we expected that clusters of host plants would be found easily by individuals dispersing from the adjacent natural patch. As expected, over 90% of the experimental host plant clusters were discovered over the course of the season, but the dogbane beetles visiting the clusters of host plants we added were likely long-distance dispersers (> 350 m), given that we found no marked dogbane beetles from the natural patch in any of the plant clusters. We found no effect of the stepping stone anangement on the number of dogbane beetles captured in the clusters. Furthermore, dogbane beetles only visited the host plant clusters for a short time, presumably to feed and rest, rather than taking up residence and laying egg masses as they did on host plants in natural patches. Preliminary evidence supported the hypothesis that patches of A. cannabinum might serve as stepping stones for dogbane beetles moving among large populations of the host plant. For dogbane beetles and other prairie insects dependent on plants found in scattered remnants, small, frequently unoccupied patches might facilitate movement between large patches even though they might not support viable populations.
Biological Journal of the Linnean Society, 1987
Page 1. Biologzcal Journal of the Linnean SocieQ (1987) 31: 59-74. With 1 figure Plants and insec... more Page 1. Biologzcal Journal of the Linnean SocieQ (1987) 31: 59-74. With 1 figure Plants and insects in early old-field succession: comparison of an English site and an American site VALERIE K. BROWN Department of Pure ...
Agriculture, Ecosystems & Environment, 2008
... Kyle S. Kwaiser 1 , a and Stephen D. Hendrix Corresponding Author Contact Information , a , E... more ... Kyle S. Kwaiser 1 , a and Stephen D. Hendrix Corresponding Author Contact Information , a , E-mail The Corresponding Author. ... There was also a preference for human-yellow flowers after adjusting for ramet abundance and there were significantly more bees caught in yellow ...
The Journal of Animal Ecology, 1988
... 1060 Page 9. SD HENDRIX, VK BROWN AND H. DINGLE Silwood Year I - . -.-a&amp;quot;&amp... more ... 1060 Page 9. SD HENDRIX, VK BROWN AND H. DINGLE Silwood Year I - . -.-a&amp;quot;&amp;quot;i II 3Ct&amp;#x27; M J J A S 0 Year 2 i / x ??&amp;quot;..n-C]...n . . -n-... . MJ J AS 0 // .:_.. ... (a) total phytophages (0---0), chewers (O-1-o), sap-feeders (A-- -); b) tourists (o---o), parasitoids (0--0), predators (A---A). ...
Journal of economic entomology, Jan 28, 2018
Almond (Prunus dulcis (Mill.) D. A. Webb; Rosales: Rosaceae) is a cash crop with an estimated glo... more Almond (Prunus dulcis (Mill.) D. A. Webb; Rosales: Rosaceae) is a cash crop with an estimated global value of over seven billion U.S. dollars annually and commercial varieties are highly dependent on insect pollination. Therefore, the understanding of basic pollination requirements of the main varieties including pollination efficiency of honey bees (Apis mellifera, Linnaeus, Hymenoptera: Apidae) and wild pollinators is essential for almond production. We first conducted two lab experiments to examine the threshold number of pollen grains needed for successful pollination and to determine if varietal identity or diversity promotes fruit set and weight. Further, we examined stigma and ovules of flowers visited by Apis and non-Apis pollinators in the field to study the proportion of almond to non-almond pollen grains deposited, visitation time per flower visit, and tube set. Results indicate that the threshold for successful fertilization is around 60 pollen grains, but pollen can be ...
PloS one, 2016
Evidence of inter-species pathogen transmission from managed to wild bees has sparked concern tha... more Evidence of inter-species pathogen transmission from managed to wild bees has sparked concern that emerging diseases could be causing or exacerbating wild bee declines. While some pathogens, like RNA viruses, have been found in pollen and wild bees, the threat these viruses pose to wild bees is largely unknown. Here, we tested 169 bees, representing 4 families and 8 genera, for five common honey bee (Apis mellifera) viruses, finding that more than 80% of wild bees harbored at least one virus. We also quantified virus titers in these bees, providing, for the first time, an assessment of viral load in a broad spectrum of wild bees. Although virus detection was very common, virus levels in the wild bees were minimal-similar to or lower than foraging honey bees and substantially lower than honey bees collected from hives. Furthermore, when we experimentally inoculated adults of two different bee species (Megachile rotundata and Colletes inaequalis) with a mixture of common viruses that ...
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Papers by Stephen Hendrix