The Reproductive Success of Triturus ivanbureschi × T. macedonicus F1 Hybrid Females (Amphibia: Salamandridae).

Tijana Vučić,Milena Cvijanović,Ana Ivanović,Nikola Bajler,Maja Ajduković

doi:10.3390/ani12040443

Tijana Vučić, Milena Cvijanović + Show 3 more

Open Access

https://doi.org/10.3390/ani12040443

Copy DOI

Abstract

Simple SummaryTwo moderately related large-bodied newt species endemic to the Balkan Peninsula, the Balkan crested newt (Triturus ivanbureschi) and the Macedonian crested newt (T. macedonicus), coexist and hybridize in central Serbia. Many generations of mutual hybrid crossings and backcrossings with parental species shaped the genetic composition of hybrid populations. Natural populations have admixed nuclear DNA (nuDNA) of parental species and T. ivanbureschi mitochondrial DNA (mtDNA), which is usually maternally inherited. The mechanisms that direct gene flow and shape the first generations of hybrids could explain the formation of hybrid zones and their maintenance in nature. We followed and compared life history traits related to reproduction of the first generation of reciprocal hybrids obtained by experimental crossing. Our results suggested that possible incompatibilities between mitochondrial and nuclear genomes, which could lead to the exclusion of T. macedonicus mtDNA in natural populations, most likely act at later stages of development or subsequent hybrid generations. Results from this study add to the growing knowledge of Triturus hybrid biology and ecology, which is the baseline for conservation programs necessary to protect these highly endangered amphibians.Two large-bodied newt species, Triturus ivanbureschi and T. macedonicus, hybridize in nature across the Balkan Peninsula. Consequences of hybridization upon secondary contact of two species include species displacement and asymmetrical introgression of T. ivanbureschi mtDNA. We set an experimental reciprocal cross of parental species and obtained two genotypes of F1 hybrids (with T. ivanbureschi or T. macedonicus mtDNA). When hybrids attained sexual maturity, they were engaged in mutual crossings and backcrossing with parental species. We followed reproductive traits over two successive years. Our main aim was to explore the reproductive success of F1 females carrying different parental mtDNA. Additionally, we tested for differences in reproductive success within female genotypes depending on the crossing with various male genotypes (hybrids or parental species). Both female genotypes had similar oviposition periods, number of laid eggs and hatched larvae but different body and egg sizes. Overall reproductive success (percentage of egg-laying females and viability of embryos) was similar for both genotypes. The type of crossing led to some differences in reproductive success within female genotypes. The obtained results suggest that processes that led to exclusion of T. macedonicus mtDNA in natural populations may be related to the survival at postembryonic stages of F2 generation or reproductive barriers that emerged in subsequent hybrid generations.

Highlights

The reproduction of genetically divergent taxa is a frequent phenomenon in natural populations (e.g., [1,2])
The obtained results suggest that processes that led to exclusion of T. macedonicus mtDNA in natural populations may be related to the survival at postembryonic stages of F2 generation or reproductive barriers that emerged in subsequent hybrid generations
Individuals of T. ivanbureschi and T. macedonicus were collected from natural populations away from their contact zones: T. ivanbureschi from Zli Dol, Serbia (42◦25 N; 22◦27 E) with permission obtained from the Serbian Ministry of Energy, Development and Environmental Protection and T. macedonicus in Ceklin, Montenegro (42◦21 N; 18◦59 E) with permission obtained from the Agency for Environmental Protection, Montenegro

Summary

Introduction

The reproduction of genetically divergent taxa is a frequent phenomenon in natural populations (e.g., [1,2]). Hybrids could be sterile or produce further generations by mutual crossings and/or backcrossing with parental genotypes. The aforementioned outcomes of hybridization are largely dependent on the phylogenetic relatedness of parental species and/or the time of divergence from the most common ancestor. The hybrid breakdown could be expected in the second or even in subsequent generations as a result of an accumulation of incompatibilities that produce reproductive barriers. Hybridization between phylogenetically more divergent taxa could result in largely decreased viability or sterility of one or both sexes of F1 hybrids [6,9,10,11,12,13,14,15,16,17]. For mito-nuclear incompatibilities, the Dobzhansky–Muller model was proposed as the most probable model of the evolution of incompatibilities (see [18] and references therein)

Methods

Results

Discussion

Conclusion