Importance of Hybrids of <i>Meccus phyllosomus mazzottii</i>, and <i>M. p. pallidipennis</i>, and <i>M. p. phyllosomus</i> to the Transmission of <i>Trypanosoma cruzi</i> in Mexico
Abstract:SUMMARY: The time interval before beginning feeding, feeding time, and defecation delay for 3 Triatominae subspecies, Meccus phyllosomus mazzottii (Ma), M. p. pallidipennis (Pa), and M. p. phyllosomus (Phy) and their laboratory hybrids were evaluated. The mean time interval for beginning feeding was between 0.1 and 10.1 min for all nymphal instars in each cohort, with significant (P ＜ 0.05) differences among hybrids and parental cohorts. Four (both MaPa and MaPhy) hybrid cohorts had similar mean feeding times … Show more
“…In addition, Mexican triatomine F1 hybrids also resulted in F1 offspring that were morphologically indistinguishable from one of the parental lines [ 39 ] and in second-generation hybrids (F2) with phenotypic characteristics either specific to those of one of the parents or with intermediate characteristics [ 40 , 41 ]. Considering that some factors can result in an increased risk of T. cruzi transmission to humans and animals (such as vigor [ 42 ] and hybrid fitness [ 43 ]) and that recently it has been reported that hybrids of the T. phyllosoma subcomplex show greater potential to acquire and transmit T. cruzi than parental species [ 44 , 45 ], the study of segregation of external morphology can also be of epidemiological importance [ 37 , 38 ]. Fig.…”
Background
The tribe Rhodniini is a monophyletic group composed of 24 species grouped into two genera: Rhodnius and Psammolestes. The genus Psammolestes includes only three species, namely P. coreodes, P. tertius and P. arthuri. Natural hybridization events have been reported for the Rhodniini tribe (for genus Rhodnius specifically). Information obtained from hybridization studies can improve our understanding of the taxonomy and systematics of species. Here we report the results from experimental crosses performed between P. tertius and P. coreodes and from subsequent analyses of the reproductive and morphological aspects of the hybrids.
Methods
Crossing experiments were conducted between P. tertius and P. coreodes to evaluate the pre- and post-zygotic barriers between species of the Rhodniini tribe. We also performed cytogenetic analyses of the F1 hybrids, with a focus on the degree of pairing between the homeologous chromosomes, and morphology studies of the male gonads to evaluate the presence of gonadal dysgenesis. Lastly, we analyzed the segregation of phenotypic characteristics.
Results
Interspecific experimental crosses demonstrated intrageneric genomic compatibility since hybrids were produced in both directions. However, these hybrids showed a high mortality rate, suggesting a post-zygotic barrier resulting in hybrid unviability. The F1 hybrids that reached adulthood presented the dominant phenotypic segregation pattern for P. tertius in both directions. These insects were then intercrossed; the hybrids were used in the cross between P. tertius ♀ × P. coreodes ♂ died before oviposition, and the F1 hybrids of P. coreodes ♀ x P. tertius ♂ oviposited and their F2 hybrids hatched (however, all specimens died after hatching, still in first-generation nymph stage, pointing to a hybrid collapse event). Morphological analyses of male gonads from F1 hybrids showed that they did not have gonadal dysgenesis. Cytogenetic analyses of these triatomines showed that there were metaphases with 100% pairing between homeologous chromosomes and metaphases with pairing errors.
Conclusion
The results of this study demonstrate that Psammolestes spp. have intrageneric genomic compatibility and that post-zygotic barriers, namely unviability of hybrid and hybrid collapse, resulted in the breakdown of the hybrids of P. tertius and P. coreodes, confirming the specific status of species based on the biological concept of species.
Graphical abstract
“…In addition, Mexican triatomine F1 hybrids also resulted in F1 offspring that were morphologically indistinguishable from one of the parental lines [ 39 ] and in second-generation hybrids (F2) with phenotypic characteristics either specific to those of one of the parents or with intermediate characteristics [ 40 , 41 ]. Considering that some factors can result in an increased risk of T. cruzi transmission to humans and animals (such as vigor [ 42 ] and hybrid fitness [ 43 ]) and that recently it has been reported that hybrids of the T. phyllosoma subcomplex show greater potential to acquire and transmit T. cruzi than parental species [ 44 , 45 ], the study of segregation of external morphology can also be of epidemiological importance [ 37 , 38 ]. Fig.…”
Background
The tribe Rhodniini is a monophyletic group composed of 24 species grouped into two genera: Rhodnius and Psammolestes. The genus Psammolestes includes only three species, namely P. coreodes, P. tertius and P. arthuri. Natural hybridization events have been reported for the Rhodniini tribe (for genus Rhodnius specifically). Information obtained from hybridization studies can improve our understanding of the taxonomy and systematics of species. Here we report the results from experimental crosses performed between P. tertius and P. coreodes and from subsequent analyses of the reproductive and morphological aspects of the hybrids.
Methods
Crossing experiments were conducted between P. tertius and P. coreodes to evaluate the pre- and post-zygotic barriers between species of the Rhodniini tribe. We also performed cytogenetic analyses of the F1 hybrids, with a focus on the degree of pairing between the homeologous chromosomes, and morphology studies of the male gonads to evaluate the presence of gonadal dysgenesis. Lastly, we analyzed the segregation of phenotypic characteristics.
Results
Interspecific experimental crosses demonstrated intrageneric genomic compatibility since hybrids were produced in both directions. However, these hybrids showed a high mortality rate, suggesting a post-zygotic barrier resulting in hybrid unviability. The F1 hybrids that reached adulthood presented the dominant phenotypic segregation pattern for P. tertius in both directions. These insects were then intercrossed; the hybrids were used in the cross between P. tertius ♀ × P. coreodes ♂ died before oviposition, and the F1 hybrids of P. coreodes ♀ x P. tertius ♂ oviposited and their F2 hybrids hatched (however, all specimens died after hatching, still in first-generation nymph stage, pointing to a hybrid collapse event). Morphological analyses of male gonads from F1 hybrids showed that they did not have gonadal dysgenesis. Cytogenetic analyses of these triatomines showed that there were metaphases with 100% pairing between homeologous chromosomes and metaphases with pairing errors.
Conclusion
The results of this study demonstrate that Psammolestes spp. have intrageneric genomic compatibility and that post-zygotic barriers, namely unviability of hybrid and hybrid collapse, resulted in the breakdown of the hybrids of P. tertius and P. coreodes, confirming the specific status of species based on the biological concept of species.
Graphical abstract
“…These three subspecies have been inter-crossed with each other under laboratory and wild conditions, and fertile hybrids have been obtained (Martínez-Ibarra et al ., 2008 b , 2009). Some triatomine laboratory hybrids have displayed intermediate characteristics or have shown outstanding biological parameters that may confer higher fitness than their parental species (Almeida et al ., 2012; Chávez-Contreras et al ., 2013, Martínez-Ibarra et al ., 2015 b , c ). Wild hybrids have also been associated with resistance to insecticides or have shown higher entomological indices than ‘pure’ species collected (Martínez-Ibarra et al ., 2008 a ; Mas-Coma & Bargues, 2009).…”
Understanding the biological parameters of some triatomine subspecies of Meccus phyllosomus (Burmeister) is a crucial first step in estimating the epidemiological importance of this group. Biological parameters related to egg eclosion, egg-to-adult development time, number of blood meals to moult, percentage of females at the end of the cycle, number of laid eggs, and the accumulative mortality for each instar of three M. phyllosomus subspecies [Meccus phyllosomus pallidipennis (Stål), Meccus phyllosomus longipennis (Usinger), and Meccus phyllosomus picturatus (Usinger)] as well as their laboratory hybrids were evaluated and compared. No significant differences (P > 0.05) were recorded among the experimental hybrids (M. p. longipennis × M. p. pallidipennis, M. p. longipennis × M. p. picturatus, M. p. pallidipennis × M. p. picturatus) and reciprocal cohorts. In five of the six studied parameters (egg eclosion, egg-to-adult development time, number of blood meals to moult, number of laid eggs and accumulative mortality), with the exception of the non-significant percentage of females obtained among all the studied cohorts, at least one of the parental cohorts in each set of crosses exhibited better fitness results than by those of their hybrid descendants. The lack of hybrid fitness in our study indicates the maintenance of reproductive isolation of parental genotypes. Moreover, the results lead us to propose that an incipient speciation process by distance is currently developing among the three studied subspecies, increasing the differences between them that modify the transmission efficiency of Trypanosoma cruzi to human beings in Mexico.
“…En dos estudios recientes (10,11) sobre los pará-metros biológicos de los híbridos de grupos filogenéticamente cercanos, se ha demostrado el vigor híbrido de los descendientes, con el consecuente aumento del riesgo de transmisión de T. cruzi a las poblaciones humanas. Por ello, el objetivo de este estudio fue conocer los parámetros biológicos de los parentales de T. recurva, M. p. phyllosomus y de sus descendientes.…”
Introducción. Los híbridos de especies y subespecies de triatominos mexicanos exhiben características biológicas y de comportamiento sobresalientes comparadas con las de sus parentales, específicamente su vigor híbrido, lo cual puede incrementar el riesgo de transmisión de Trypanosoma cruzi a sus huéspedes humanos y animales.Objetivo. Describir y comparar los valores de los parámetros biológicos relacionados con el ciclo de vida de Triatoma recurva, de Meccus phyllosomus phyllosomus y de sus híbridos de laboratorio, para estimar su riesgo como transmisores de T. cruzi a las poblaciones humanas.Materiales y métodos. Se entrecruzaron ejemplares de T. recurva y de M. p. phyllosomus y se obtuvo una cohorte híbrida. Las tres cohortes se mantuvieron bajo condiciones similares de laboratorio. En las tres se compararon los datos de sus ciclos de vida, el número de alimentaciones necesarias para mudar, el porcentaje de mortalidad, el de eclosión de huevos y la fecundidad de las hembras.Resultados. La cohorte híbrida tuvo el menor tiempo promedio entre el primer instar o estadio y el adulto (136,6 ± 17,5 días). El número de alimentaciones para cambiar de instar (13,4 ± 1,7; 15,6 ± 5,2) fue mayor en la cohorte híbrida y en la de T. recurva. La cohorte híbrida registró la menor mortalidad (29 %) y el mayor porcentaje (70 %) de hembras al final del ciclo biológico. La fecundidad por hembra por día (rango: 1,1 ± 0,6 -1,6 ± 0,7) fue similar entre las poblaciones. El porcentaje de eclosión de huevos fue superior a 70 % en la cohorte híbrida y en la de M. p. phyllosomus.Conclusión. La cohorte híbrida presentó algunas características biológicas que implicarían un mayor poder transmisor de T. cruzi que el de sus grupos parentales.
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