scholarly journals Testing the Role of Habitat Isolation among Ecologically Divergent Gall Wasp Populations

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Scott P. Egan ◽  
Glen R. Hood ◽  
James R. Ott
Keyword(s):  
Reproductive Isolation ◽  
Assortative Mating ◽  
Host Plants ◽  
Habitat Preferences ◽  
Habitat Isolation ◽  
Native Plant ◽  
Gall Wasp ◽  
Quercus Virginiana ◽  
Respective Host

Habitat isolation occurs when habitat preferences lower the probability of mating between individuals associated with differing habitats. While a potential barrier to gene flow during ecological speciation, the effect of habitat isolation on reproductive isolation has rarely been directly tested. Herein, we first estimated habitat preference for each of six populations of the gall waspBelonocnema treataeinhabiting eitherQuercus virginianaorQ. geminata. We then estimated the importance of habitat isolation in generating reproductive isolation betweenB. treataepopulations that were host specific to eitherQ. virginianaorQ. geminataby measuring mate preference in the presence and absence of the respective host plants. All populations exhibited host preference for their native plant, and assortative mating increased significantly in the presence of the respective host plants. This host-plant-mediated assortative mating demonstrates that habitat isolation likely plays an important role in promoting reproductive isolation among populations of this host-specific gall former.

Separation of various Frankia strains in the Alnus and Elaeagnus host specificity groups using sugar analysis

1987 ◽  
Vol 33 (9) ◽  
pp. 764-772 ◽  
Author(s):  
L. St-Laurent ◽  
J. Bousquet ◽  
L. Simon ◽  
M. Lalonde
Keyword(s):  
Gas Chromatography ◽  
Host Specificity ◽  
Host Plants ◽  
Sugar Content ◽  
Statistical Analyses ◽  
Myrica Gale ◽  
Trimethylsilyl Derivatives ◽  
Derivatives Of ◽  
Respective Host

To confirm the role of glycosides in the taxonomy of Frankia, 79 strains initially isolated from Alnus spp., Myrica spp., Comptonia sp., Elaeagnus spp., Shepherdia spp., and Hippophaë sp. host plants were tested for relative sugar content after 2 and 8 weeks of growth. Gas chromatography was used to separate the trimethylsilyl derivatives of sugars present in whole-cell hydrolysates of the Frankia strains; six sugars were quantitatively analyzed including 2-O-methyl-D-mannose, a sugar ubiquitous in the genus Frankia. The separation of the Frankia strains into their appropriate host specificity group (Alnus or Elaeagnus), based only on the sugar content, was achieved using statistical analyses of observations at 2 and 8 weeks. All statistical analyses correlated together and showed a significant separation between both host specificity groups. 2-O-Methyl-D-mannose, the concentration of which varied greatly between the Alnus and Elaeagnus host specificity groups, was the most discriminant sugar. Moreover, it was constant at both ages. From discriminant analysis, the separation of the various Frankia strains tested into their respective host specificity group was more precise at 2 weeks with a classification success of 97%, as compared with 78% at 8 weeks. The Myrica gale isolates that nodulated host plants from both host specificity groups were generally intermediate in their sugar content between the Alnus and Elaeagnus host specificity groups.

scholarly journals The role of multiple reproductive barriers: strong post-pollination interactions govern cytotype isolation in a tetraploid–octoploid contact zone

2020 ◽  
Vol 126 (6) ◽  
pp. 991-1003 ◽  
Author(s):  
Mariana Castro ◽  
João Loureiro ◽  
Brian C Husband ◽  
Sílvia Castro
Keyword(s):  
Reproductive Isolation ◽  
Contact Zone ◽  
Assortative Mating ◽  
Reproductive Barriers ◽  
Pollinator Behaviour ◽  
Contact Zones ◽  
Foraging Preferences ◽  
Flowering Asynchrony ◽  
Gametic Selection

Abstract Background and Aims Polyploidy is an important contributor to sympatric speciation and assortative mating is a key mechanism driving cytotype interactions in contact zones. While strong reproductive barriers can mediate the coexistence of different cytotypes in sympatry, positive frequency-dependent mating disadvantage ultimately drives the transition to single-ploidy populations. However, comprehensive estimates of reproductive isolation among cytotypes and across multiple barriers are rare. We quantify the strength of isolation across multiple reproductive stages in a tetraploid–octoploid contact zone to understand the potential for coexistence. Methods Assortative mating due to flowering asynchrony, pollinator behaviour, morphological overlap, self-fertilization and gametic competition between tetraploid and octoploid Gladiolus communis in a contact zone in the Western Iberian Peninsula were assessed in natural and experimental populations to quantify reproductive isolation (RI) between cytotypes. Key Results Tetraploids and octoploids have a high degree of overlap in flowering time and similar floral morphology, and are visited by generalist insects without cytotype foraging preferences, resulting in weak pre-pollination RI (from 0.00 to 0.21). In contrast, post-pollination isolation resulting from gametic selection was a strong barrier to inter-cytotype mating, with ploidy composition in stigmatic pollen loads determining the levels of RI (from 0.54 to 1.00). Between-cytotype cross-incompatibility was relatively high (RI from 0.54 to 0.63) as was isolation acquired through self-pollination (RI of 0.59 in tetraploids and 0.39 in octoploids). Conclusions Total RI was high for both tetraploids (from 0.90 to 1.00) and octoploids (from 0.78 to 0.98). Such high rates of assortative mating will enable cytotype coexistence in mixed-ploidy populations by weakening the impacts of minority cytotype exclusion. This study reveals the key role of gametic selection in cytotype siring success and highlights the importance of comprehensive estimates across multiple reproductive barriers to understand cytotype interactions at contact zones.

Assortative mating and divergent male courtship behaviours between two cryptic species of nine-spined sticklebacks (genus Pungitius)

Behaviour ◽  
2016 ◽  
Vol 153 (15) ◽  
pp. 1879-1911 ◽  
Author(s):  
Yu-ichiro Meguro ◽  
Hiroshi Takahashi ◽  
Yoshiyasu Machida ◽  
Hokuto Shirakawa ◽  
Michelle R. Gaither ◽  
...  
Keyword(s):  
Reproductive Isolation ◽  
Cryptic Species ◽  
Assortative Mating ◽  
Brackish Water ◽  
Courtship Behaviour ◽  
Water Type ◽  
Male Courtship ◽  
Future Studies ◽  
Kinematic Analyses

Assortative mating based on ecologically divergent traits is a major driver of speciation among three-spined sticklebacks, however, little is known about reproductive isolation and variations in courtship behaviour among nine-spined sticklebacks. Here we demonstrate assortative mating and divergent courtship behaviours between two cryptic species of nine-spined sticklebacks using no-choice mate trials and kinematic analyses. Strong assortative mating was demonstrated in our tank experiments, highlighting the importance of prezygotic reproductive isolation in these species. Kinematic analyses showed that the freshwater type exhibited aggressive courtship behaviour with frequent ‘Attacking’ and spent more time exhibiting displacement activities. In contrast, the brackish-water type demonstrated a higher frequency of the ‘Zigzag-dance’ and ‘Nest-showing’. Our study highlights the value of nine-spined sticklebacks as a comparative system for the study of speciation and paves the way for future studies on the role of courtship behaviours and assortative mating in the evolution of sticklebacks.

scholarly journals Gut microbiomes and reproductive isolation in Drosophila

2017 ◽  
Vol 114 (48) ◽  
pp. 12767-12772 ◽  
Author(s):  
Philip T. Leftwich ◽  
Naomi V. E. Clarke ◽  
Matthew I. Hutchings ◽  
Tracey Chapman
Keyword(s):  
Reproductive Isolation ◽  
Assortative Mating ◽  
Gut Microbiome ◽  
Experimental Studies ◽  
Gut Bacteria ◽  
Evolutionary Significance ◽  
Direct Role ◽  
General Role ◽  
Positive Assortative Mating

Experimental studies of the evolution of reproductive isolation (RI) in real time are a powerful way in which to reveal fundamental, early processes that initiate divergence. In a classic speciation experiment, populations of Drosophila pseudoobscura were subjected to divergent dietary selection and evolved significant positive assortative mating by diet. More recently, a direct role for the gut microbiome in determining this type of RI in Drosophila melanogaster has been proposed. Manipulation of the diet, and hence the gut microbiome, was reported to result in immediate assortative mating by diet, which could be eliminated by reducing gut microbes using antibiotics and recreated by adding back Lactobacillus plantarum. We suggest that the evolutionary significance of this result is unclear. For example, in D. melanogaster, the microbiome is reported as flexible and largely environmentally determined. Therefore, microbiome-mediated RI would be transient and would break down under dietary variation. In the absence of evolutionary coassociation or recurrent exposure between host and microbiome, there are no advantages for the gut bacteria or host in effecting RI. To explore these puzzling effects and their mechanisms further, we repeated the tests for RI associated with diet-specific gut microbiomes in D. melanogaster. Despite observing replicable differences in the gut microbiomes of flies maintained on different diets, we found no evidence for diet-associated RI, for any role of gut bacteria, or for L. plantarum specifically. The results suggest that there is no general role for gut bacteria in driving the evolution of RI in this species and resolve an evolutionary riddle.

scholarly journals Diversity, Host Ranges, and Potential Drivers of Speciation Among the Inquiline Enemies of Oak Gall Wasps (Hymenoptera: Cynipidae)

2020 ◽  
Vol 4 (6) ◽  
Author(s):  
Anna K G Ward ◽  
Sofia I Sheikh ◽  
Andrew A Forbes
Keyword(s):  
Reproductive Isolation ◽  
Gall Wasp ◽  
Wasp Species ◽  
Host Shifts ◽  
The North ◽  
Trade Offs ◽  
Gall Wasps ◽  
Oak Tree ◽  
New Hosts

Abstract Animals that exploit living spaces of other animals (inquilines) may have specialized traits that adapt them to extended phenotypes of their ‘hosts’. These adaptations to host traits may incur fitness trade-offs that restrict the host range of an inquiline such that shifts to new hosts might trigger inquiline diversification. Speciation via host shifting has been studied in many animal parasites, but we know less about the role of host shifts in inquiline speciation. Synergus Hartig (Hymenoptera: Cynipidae: Synergini) is a speciose but taxonomically challenging genus of inquilines that feed inside galls induced by oak gall wasps (Hymenoptera: Cynipidae: Cynipini). Here, we report on a large collection of Synergus reared from galls of 33 oak gall wasp species in the upper Midwestern United States. We integrated DNA barcodes, morphology, ecology, and phenology to delimit putative species of Synergus and describe their host ranges. We find evidence of at least 23 Synergus species associated with the 33 gall wasp hosts. At least five previously described Synergus species are each complexes of two to five species, while three species fit no prior description. We find evidence that oak tree phylogeny and host gall morphology define axes of specialization for Synergus. The North American Synergus have experienced several transitions among gall hosts and tree habitats and their host use is correlated with reproductive isolation. It remains too early to tell whether shifts to new hosts initiate speciation events in Synergus inquilines of oak gall wasps, or if host shifts occur after reproductive isolation has already evolved.

The role of breeding behavior and habitat preferences on the reproductive isolation of three allopatric populations of ninespine stickleback, Pungitius pungitius

1977 ◽  
Vol 55 (10) ◽  
pp. 1601-1611 ◽  
Author(s):  
John R. Foster
Keyword(s):  
Assortative Mating ◽  
Habitat Preferences ◽  
Breeding Behavior ◽  
Pungitius Pungitius ◽  
Nest Location ◽  
Ninespine Stickleback ◽  
Positive Assortative Mating ◽  
Size Type ◽  
Nesting Substrate

Earlier studies have shown differences in morphology and reproductive behavior of Mississippi, Bering, and European populations of ninespine stickleback (Pungitius pungitius). In this study, assortative mating was examined experimentally to determine the role of habitat preference and breeding behavior as possible isolating mechanisms. Choice tests in naturalistic and uniform environments showed positive assortative mating in all but one pairing. One-hour latency tests gave similar results, while in the 24-h latency tests, interpopulation mating became prevalent. Although nesting habitat selection differences were found, courtship breakoff appeared to be a more important isolating mechanism. Failure to induce females to court was probably due to differences in male color, size, body proportions, and zigzag display. Failure to lead the female to the nest was probably related to differences in color and leading behavior, while failure to induce the female to enter the nest was probably related to differences in nesting substrate, nest location, and size, type, and number of entrances. The results of this study demonstrate that reproductive divergence among the three populations makes intrapopulation mating more likely than interpopulation mating.

scholarly journals Divergent host-plant use promotes reproductive isolation among cynipid gall wasp populations

2012 ◽  
Vol 8 (4) ◽  
pp. 605-608 ◽  
Author(s):  
Scott P. Egan ◽  
Glen R. Hood ◽  
Jeff L. Feder ◽  
James R. Ott
Keyword(s):  
Reproductive Isolation ◽  
Host Plant ◽  
Sexual Isolation ◽  
Host Use ◽  
Gall Wasp ◽  
Allopatric Populations ◽  
Divergent Natural Selection ◽  
Quercus Virginiana ◽  
Host Plant Use ◽  
Quercus Geminata

Ecological speciation occurs when reproductive isolation evolves as a consequence of divergent natural selection among environments. A direct prediction of this process is that ecologically divergent pairs of populations will exhibit greater reproductive isolation than ecologically similar pairs of populations. By comparing allopatric populations of the cynipid gall wasp Belonocnema treatae infesting Quercus virginiana and Quercus geminata , we tested the role that divergent host use plays in generating ecological divergence and sexual isolation. We found differences in body size and gall structure associated with divergent host use, but no difference in neutral genetic divergence between populations on the same or different host plant. We observed significant assortative mating between populations from alternative host plants but not between allopatric populations on the same host plant. Thus, we provide evidence that divergent host use promotes speciation among gall wasp populations.

scholarly journals What shapes the continuum of reproductive isolation? Lessons from Heliconius butterflies

2017 ◽  
Author(s):  
C. Mérot ◽  
C. Salazar ◽  
R. M. Merrill ◽  
C. Jiggins ◽  
M. Joron
Keyword(s):  
Gene Flow ◽  
Mate Choice ◽  
Reproductive Isolation ◽  
Hybrid Sterility ◽  
Habitat Isolation ◽  
Wing Pattern ◽  
Key Factor ◽  
Comparative Results ◽  
Phylogenetic Divergence

AbstractThe process by which species evolve can be illuminated by investigating barriers that limit gene flow between taxa. Recent radiations, such as Heliconius butterflies, offer the opportunity to compare isolation between pairs of taxa at different stages of ecological, geographic and phylogenetic divergence. We carry out a comparative analysis of existing and novel data in order to quantify the strength and direction of isolating barriers within a well-studied clade of Heliconius. Our results highlight that increased divergence is associated with the accumulation of stronger and more numerous barriers to gene flow. Wing pattern is both under natural selection for Müllerian mimicry and involved in mate choice, and therefore underlies several isolating barriers. However, pairs which share a similar wing pattern, also display strong reproductive isolation mediated by traits other than wing pattern. This suggests that, while wing pattern is a key factor for early stages of divergence, it is not essential at a higher level. Additional factors including habitat isolation, hybrid sterility and chemically-mediated mate choice are associated with complete speciation. Therefore, although most previous work has emphasised the role of wing pattern, our comparative results highlight that speciation is a multidimensional process, whose completion is stabilized by many factors.

scholarly journals Larval Performance in the Context of Ecological Diversification and Speciation inLycaeidesButterflies

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Cynthia F. Scholl ◽  
Chris C. Nice ◽  
James A. Fordyce ◽  
Zachariah Gompert ◽  
Matthew L. Forister
Keyword(s):  
Reproductive Isolation ◽  
Host Plants ◽  
Oviposition Preference ◽  
Ecological Speciation ◽  
Larval Performance ◽  
Ecological Traits ◽  
Ecological Diversification ◽  
Behavioral Traits ◽  
Plant Effects

The role of ecology in diversification has been widely investigated, though few groups have been studied in enough detail to allow comparisons of different ecological traits that potentially contribute to reproductive isolation. We investigated larval performance within a species complex ofLycaeidesbutterflies. Caterpillars from seven populations were reared on five host plants, asking if host-specific, adaptive larval traits exist. We found large differences in performance across plants and fewer differences among populations. The patterns of performance are complex and suggest both conserved traits (i.e., plant effects across populations) and more recent dynamics of local adaptation, in particular forL. melissathat has colonized an exotic host. We did not find a relationship between oviposition preference and larval performance, suggesting that preference did not evolve to match performance. Finally, we put larval performance within the context of several other traits that might contribute to ecologically based reproductive isolation in theLycaeidescomplex. This larger context, involving multiple ecological and behavioral traits, highlights the complexity of ecological diversification and emphasizes the need for detailed studies on the strength of putative barriers to gene flow in order to fully understand the process of ecological speciation.

Sign in / Sign up

Export Citation Format

Share Document