Sex wars: a female genital spine forces male damselflies to shorten copulation duration

In some species, males use weapons to harm females, increasing their short-term fitness. Here we show that females can use genital adaptations against males. Females of the damselfly Enallagma cyathigerum have a conspicuous vulvar spine on the eighth abdominal segment, which contacts with the male during copulation. We tested 3 hypotheses for its function: it (a) inflicts damage to the male during copulation; (b) facilitates endophytic oviposition; and (c) stimulates males during copulation to increase their investment. We found that males mated on average for 54 min with control females, but increased copulation to 99 min with females without spine. There was no evidence of physical harm of the spine on the male’s seminal vesicle, which shows 8- to 18-folds, exactly where the spine contacts during copulation. Females with and without spine exhibited the same egg-laying rates and showed similar fecundity and fertility. Longevity was also similar in males mated to control and spineless females. In contrast to many species where females resist male harassment by behavioral responses, the morphological adaptation observed in E. cyathigerum appears to act as a sexual weapon, allowing females to control copulation duration. We suggest that the spine has evolved because of sexual conflict over mating duration.Universidade de Vigo/CISUGMinisterio de Economía y Competitividad | Ref. CGL2014-53140-PAgencia Estatal de Investigación | Ref. PGC2018-096656-B-I0

Evolution in Islands: contrasting morph frequencies in damselfly populations of the Balearic Islands

Colour polymorphism is an example of visible phenotypic variability that is often associated with ecological factors and may produce local adaptations. Small populations, particularly in islands, offer opportunities for evolutionary novelties, and are therefore of particular interest to the study of polymorphisms. Here we study the dynamics of female colour morphs in the damselfly Ischnura elegans in the Balearic Islands. We found that insular populations are small, show low density, low mating activity, and low androchrome frequency. Our surveys suggest that male harassment is a powerful force in the dynamics of this female-limited polymorphism, because high male densities result in lower presence of mature females around the water, where copulation takes place. Non-male-like (infuscans) females have higher mating frequency. Androchromes were rare (15%) in all populations, but the frequency of the two non-male like females (infuscans and aurantiaca) was reversed between islands, despite their geographical proximity. We found a possible novel morph, suggesting that insular conditions allow innovations. Fitness differences between the two non-male-like females of I. elegans are still understudied, because most previous research has concentrated on the maintenance of androchromes, and are therefore a priority for future research.Agencia Estatal de Investigación | Ref. PGC2018-096656-B-I00Universidade de Vigo/CISU

The evolution and diversity of intra-male sperm translocation in Odonata: a unique behaviour in animals

Behavioural diversity is a basic component of biodiversity, with implications in ecological interactions at the intra- and interspecific levels. The reproductive behaviour of Odonata (dragonflies and damselflies) is unique among insects and conditioned by the anatomical separation between the male’s reproductive organs and the intromittent organ. Prior to mating, males must translocate sperm from the genital pore in the ninth abdominal segment to the seminal vesicle located ventrally in the second abdominal segment. This behaviour, exclusive to odonates, is known as intra-male sperm translocation (ST). Here, we review the literature on ST and use phylogenetic comparative analyses to investigate the evolution of ST within the Odonata. Information on ST was compiled for 176 species, with the commonest variant being ST once per mating, after tandem formation (66%). Other variants found were ST involving precopulatory genital touching (10%), ST by the male alone before tandem (16%) or after copulation (5%), and repetition of ST during the same copulation (3%). The precopulatory genital touching might have evolved to detect female receptivity. ST before tandem formation might be favoured when mating opportunities are scarce and copulations are brief. ST after mating might be favoured if males need to be ready to copulate fast. Finally, repeated ST could have evolved through postcopulatory sexual selection in males with limited sperm removal ability, as a means to improve their sperm competition. The most plausible scenario for the evolution of ST is that the ancestors of the Odonata produced a spermatophore and attached it to the body, leading towards the evolution of the secondary genitalia in males. Our study emphasises the role of behavioural diversity to understand behavioural evolution.Ministerio de Economía y Competitividad | Ref. BES-2015-071965Ministerio de Economía y Competitividad | Ref. CGL2014-53140-

Sexual conflict and the evolution of monandry: the case of the damselfly Ischnura hastata (Odonata: Coenagrionidae) in the Galápagos Islands

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUG1. Sexual selection favours the evolution and maintenance of polygamy, which is the dominant reproductive strategy in insects. Monogamy can evolve in very short-lived species due to time constraints. Here we study adult activity and mating behaviour of a population of the damselfly Ischnura hastata, a species rarely seen mating, and which has been suggested to be monandric, in wetlands of Isabela Island, Galápagos. 2. By means of mark-recapture methods we estimated that the daily survival rate was low, ranging from 0.385 to 0.876, yielding average life expectancies of mature individuals of only 1.2-3.2 days. Adults showed very low activity before 7:00, indicating that mating does not occur early. The number of male-female interactions and mating attempts was extremely low, with only 44 copulations recorded on over 230 h of observations. 3. Copulations were brief, with a mean duration of 11 minutes (but only two observed from the start). Males showed clear preference to attempt to grasp in tandem females of intermediate age (in 94.3% of cases), rather than young (31.3%) or mature females (24.0%). Males were very persistent once a tandem was achieved, retaining females for up to 139 min, but most females resisted and did not copulate. 4. We conclude that females of I. hastata show a very short time window to mate, exactly when they change colour from juvenile to mature, and live only enough to mate once. Short lifespan has selected for female monandry in I. hastata, creating an intense sexual conflict over mating rates.Ministerio de Economía y Competitividad | Ref. CGL2014-53140-PAgencia Estatal de Investigación | Ref. PGC2018-096656-B-I0

Variation in intraspecific sperm translocation behaviour in a damselfly and its consequences for sperm viability

Sperm quality and viability affect both male and female fitness. Most dragonfly and damselfly males translocate sperm from the testis to the seminal vesicle before each copulation, a behaviour known as intramale sperm translocation (ST). However, some published observations indicate that odonate males can occasionally skip ST prior to copulation. Our aim was to determine the circumstances under which males skip ST and how this might affect sperm viability. We allowed males of the damselfly Ischnura graellsii to perform ST (interrupting the copulation at this stage) and we studied ST behaviour during subsequent copulation. Males were randomly assigned to four treatments, which consisted of allowing the experimental male to copulate again 15 min or 1–3 days after his last ST. Fertility of females mated with the experimental males was analysed as a proxy for sperm viability. All males used the sperm that they translocated previously when the second mating took place 15 min after the manipulation, while the proportion of males that repeated ST increased steadily over time. Both treatment (time elapsed since last ST) and the interaction between treatment and ST (yes/no) had a significant effect on fertility, which decreased only in males that did not perform ST immediately before copulation. Additional experiments with damselflies of the genus Calopteryx showed also that males did not repeat ST when the time to the next copulation was less than a day. Our results suggest that sperm quality decays over time in odonates, and that males can choose whether to keep and reuse the sperm in the seminal vesicle or to discard it. We conclude that the special anatomical disposition of odonate males might increase selective pressures to maximize sperm viability and/or repeated intramale ST behaviour.Ministerio de Economía y Competitividad | Ref. BES-2015-071965Ministerio de Economía y Competitividad | Ref. CGL2014-53140-

Alternative reproductive strategies in black-winged territorial males of Paraphlebia zoe (Odonata, Thaumatoneuridae)

Alternative reproductive strategies are commonly associated with male dimorphism. In Paraphlebia zoe, a species of damselfly whose males are dimorphic in wing coloration, black-and-white-winged (BW) males defend territories, while hyaline-winged (HW) males usually play the role of satellites. We found that several BW males can sometimes share a territory, and we hypothesized that within this morph there are two alternative tactics: submissive and dominant. We conducted an experiment to test whether dominant and submissive roles are plastic or stable and fixed on each individual. To this end, we manipulated black and white spots of BW males in four treatments: (i) painting over white and black spots without changing their size, (ii) erasing the white spot using black painting, (iii) increasing the black spot and moving the white spot maintaining its size and (iv) control males. Additionally, we investigated the correlation between some phenotypic variables (wing asymmetry, survival and recapture probabilities) and male behaviour (in terms of quality of the territory). We found that the two behavioural roles (submissive and dominant) were not affected by the manipulative experiments, therefore suggesting that they are stable and fixed. Additionally, we found a positive correlation between body size and survival in both sexes, and a positive effect of territory quality and lifespan on mating success. Moreover, the largest and youngest BW males were the most symmetrical. We conclude that Paraphlebia zoe holds high behavioural diversity, with two types of strategies in BW males, dominant and submissive. The occurrence of this intra-morph behavioural diversity might depend on demographic factors such as population density and/or the relative frequency of the different morphs

Nesobasis rito sp. nov. (Zygoptera: Coenagrionidae), a new species of forest damselfly from Vanua Levu, Fiji

Nesobasis rito sp. nov. (Holotype ♂, Fiji, Vanua Levu, Drawa, 31 v 2018, A. Rivas-Torres leg.) from the comosa group is here described, illustrated, diagnosed, and compared with morphologically close species of the genus. Nesobasis rito can be distinguished from its related congeners by the shape of the caudal appendages and the ligula. The most similar species are N. comosa and N. heteroneura, which, like N. rito, have the caudal appendages covered by dense setae (especially the first species), but the shape differs clearly in lateral view, with N. rito having longer and more slender appendages, and a basal tooth clearly seen in dorsal view, absent in other members of the comosa group. The specific status of the collected specimens is also supported by the results of genetic analyses, where N. rito appears as a well-supported monophyletic clade. Nesobasis rito also has a distinct distribution from its most similar congeners: it is found on Vanua Levu, while N. comosa is found on Viti Levu and the closely related N. heteroneura is found on Viti Levu and Ovalau. All species of this group are found in streams with native forest riparian vegetation on their respective islands

Etodiversity: study of variability of sexual behavior in the order Odonata

A continuación se van a describir los métodos que serán comunes en todas las actividades que serán descritas más adelante en este documento. Estimación de la riqueza de especies mediante muestreos cuantitativos. Para poder realizar este estudio se necesita un completo conocimiento de las especies de la zona, lo cual implicará la recolección de individuos para su identificación específica (máximo 10 individuos de cada especie). Captura, marcaje y suelta de los odonatos observados a lo largo de un recorrido de 100-200 m sobre una parte de un riachuelo elegido. El marcaje de los odonatos se efectúa escribiendo un número en las alas con un rotulador permanente que no altera la supervivencia ni el comportamiento del animal. El riachuelo debe presentar afluentes y zonas con claros y sombras. El procedimiento se repetirá en 2-3 riachuelos diferentes para cada ambiente (bosque/plantación), y en cada uno de ellos se medirán variables físico-químicas del agua características del cauce. Este estudio permitirá calcular la abundancia de individuos por especie y por tanto la diversidad específica, y así determinar la especie o especies potenciales para los estudios comportamentales. Estudio comportamental. Se elegirán como especies focales aquellas especies que en bosque muestren abundancia adecuada, independientemente de su abundancia en los arroyos de plantaciones. Asimismo, se elegirán en los arroyos como especies focales aquéllas que tengan una abundancia adecuada, independientemente de su abundancia en el bosque. Así pues, si se diera el caso y sería lo ideal, se elegirán como especies focales aquéllas que tanto en bosque como en los arroyos de plantaciones sus abundancias sean adecuadas para extraer resultados representativos. Además, se tendrán en cuenta las relaciones filogenéticas entre las especies de estudio, dando prioridad a las familias poco estudiadas. Estimación de la diversidad etológica. Sumatorio de la presencia de comportamientos alternativos observados a nivel intra- e inter-específico. Al observar la riqueza de comportamientos y su dependencia con determinados ambientes, este tipo de estudio permite ampliar el concepto de diversidad ecológica. Revisión bibliográfica. Para cuantificar la diversidad de los diferentes comportamientos sexuales que se irán estudiando a lo largo de los capítulos, se hará una búsqueda y revisión bibliográfica, para posteriormente contextualizar esta variabilidad dentro de un árbol filogenético. Con esto, podríamos saber cuánto de conservado está el carácter y/ o cuándo pudo haber surgido dentro del grupo de Zygoptera.Aquí serán descritos os métodos que son comúns en todas as actividades que serán descritas máis adiante. Estimación da riqueza de especies por mostraxe cuantitativa. Para realizar este estudo, é necesario un coñecemento en profundidade das especies na zona, que vai implicar a recollida de individuos para identificación específica (máximo de 10 individuos de cada especie). Captura, marcado e liberación de Odonata observada ao longo dunha distancia de 100-200 m sobre unha parte dun fluxo escollido. Odonates reserva faise escribindo un número nas ás cun marcador permanente que non altera o comportamento supervivencia ou animal. O fluxo presentará afluentes e áreas con luz e sombra. O procedemento é repetido en 2-3 correntes distintas para cada ambiente (bosque / plantación), e en cada un características físico-químicas da auga da canle son medidas variables. Este estudo pode calcular a abundancia de individuos por especies e, así, a diversidade de especies, e determinar as especies e especies potenciais para estudos de comportamento. estudo comportamental. en especies forestais que mostran abundancia axeitada, independentemente da súa abundancia en fluxos de plantacións serán seleccionados como especies focais. Eles serán elixidos neses fluxos como especies focais ter abundancia axeitada, independentemente da súa abundancia no bosque. Entón, se fose o caso e sería especies focais ideais que será elixido como aqueles que tanto bosque e plantación de regatos súas abundancias son axeitados para extraer resultados representativos. Ademais, teñen en conta as relacións filogenéticas entre especies de estudo, dando prioridade ás familias pouco estudadas.   Estimar a diversidade etológica. Suma da presenza de comportamentos alternativos observada nivel intra-específica e Inter. Ao observar a riqueza do comportamento ea súa dependencia de determinados lugares, este tipo de estudo pode estender o concepto de diversidade ecolóxica.   Revisión da literatura. Para cuantificar a diversidade dos diferentes comportamentos sexuais que serán estudados ao longo dos capítulos, haberá unha busca e revisión de literatura, para contextualizar aínda máis esa variabilidade dentro dunha árbore filoxenética. Con iso, poderiamos saber o que o personaxe é preservada e / ou cando podería xurdir dentro do grupo de libelinha.The following will describe the methods that will be common to all activities that will be described later in this document. Estimation of species richness by quantitative sampling. To be able to carry out this study, a complete knowledge of the species of the zone is necessary, which will involve the collection of individuals for their specific identification (maximum 10 individuals of each species). Capture, mark and release of the odonates observed along a course of 100-200 m over a part of a chosen creek. The marking of odonates is done by writing a number on the wings with a permanent marker that does not alter the survival or behavior of the animal. The stream must have tributaries and areas with clearings and shadows. The procedure will be repeated in 2-3 different streams for each environment (forest / plantation), and in each one of them will be measured physical-chemical variables of the water characteristic of the channel. This study will allow to calculate the abundance of individuals by species and therefore the specific diversity, and thus to determine the species or species potential for the behavioral studies. Behavioral study. Focal species will be chosen from those species that show adequate abundance in the forest, regardless of their abundance in the plantations streams. Also, in the streams as focal species will be chosen those that have an adequate abundance, regardless of its abundance in the forest. Thus, if it were to be the case and would be ideal, we will choose as focal species those that both in forest and in the streams of plantations their abundances are adequate to extract representative results. In addition, phylogenetic relationships between the study species will be taken into account, giving priority to poorly studied families.   Estimating ethological diversity. Summarize the presence of alternative behaviors observed at the intra- and inter-specific level. By observing the richness of behaviors and their dependence on certain environments, this type of study allows to expand the concept of ecological diversity.   Bibliographic review. In order to quantify the diversity of the different sexual behaviors that will be studied throughout the chapters, a search and bibliographical revision will be made, to later contextualize this variability within a phylogenetic tree. With this, we could know how much of conserved the character and / or when it could have arisen within the group of Zygoptera

Frequency Dependence and Ecological Drift Shape Coexistence of Species with Similar Niches

The coexistence of ecologically similar species might be counteracted by ecological drift and demographic stochasticity, both of which erode local diversity. With niche differentiation, species can be maintained through performance trade-offs between environments, but trade-offs are difficult to invoke for species with similar ecological niches. Such similar species might then go locally extinct due to stochastic ecological drift, but there is little empirical evidence for such processes. Previous studies have relied on biogeographical surveys and inferred process from pattern, while experimental field investigations of ecological drift are rare. Mechanisms preserving local species diversity, such as frequency dependence (e.g., rare-species advantages), can oppose local ecological drift, but the combined effects of ecological drift and such counteracting forces have seldom been investigated. Here, we investigate mechanisms between coexistence of ecologically similar but strongly sexually differentiated damselfly species (Calopteryx virgo and Calopteryx splendens). Combining field surveys, behavioral observations, experimental manipulations of species frequencies and densities, and simulation modeling, we demonstrate that species coexistence is shaped by the opposing forces of ecological drift and negative frequency dependence (rare-species advantage), generated by interference competition. Stochastic and deterministic processes therefore jointly shape coexistence. The role of negative frequency dependence in delaying the loss of ecologically similar species, such as those formed by sexual selection, should therefore be considered in community assembly, macroecology, macroevolution, and biogeography

Data from: Frequency dependence and ecological drift shape coexistence of species with similar niches

The coexistence of ecologically similar species might be counteracted by ecological drift and demographic stochasticity, both of which erode local diversity. With niche differentiation, species can be maintained through performance trade-offs between environments, but trade-offs are difficult to invoke for species with similar ecological niches. Such similar species might then go locally extinct due to stochastic ecological drift but there is little empirical evidence for such processes. Previous studies have relied on biogeographical surveys and inferred process from pattern, while experimental field investigation of ecological drift are rare. Mechanisms preserving local species diversity, such as frequency-dependence (e. g. rare-species advantages), can oppose local ecological drift, but the combined effects of ecological drift and such counteracting forces have seldom been investigated. Here, we investigate mechanisms between coexistence of ecologically similar but strongly sexually differentiated damselfly species (Calopteryx virgo and C. splendens). Combining field surveys, behavioral observations, experimental manipulations of species frequencies and densities, and simulation modelling, we demonstrate that species coexistence is shaped by the opposing forces of ecological drift and negative frequency-dependence (rare species advantage), generated by interference competition. Stochastic and deterministic processes therefore jointly shape coexistence. The role of negative frequency-dependence in delaying the loss of ecologically similar species, such as those formed by sexual selection, should therefore be considered in community assembly, macroecology, macroevolution and biogeography