Assessment of genetic and morphological differentiation among populations of the Diederik CuckooChrysococcyx caprius

Abstract

Diederik Cuckoo (Chrysococcyx caprius) is a widely distributed species that occurs south of the Sahara Desert and migrates seasonally between breeding and non-breeding sites. It is currently unknown if the species consists of a single panmictic population or if it is genetically structured. To investigate this, we analysed sequence variation in three mitochondrial and two nuclear gene regions in combination with morphological measurements in specimens from four localities. Phylogenetic relationships were estimated using maximum likelihood methods and included specimens of Klaas's Cuckoo (Chrysoccyx klaas), Red-chested Cuckoo (Cuculus solitarius) and African Cuckoo (Cuculus gularis) to characterise levels of genetic differentiation. Haplotype networks and analysis of molecular variance were used to characterize the spatial distribution of genetic diversity. Lastly, a principal component analysis was performed to investigate morphological variation among localities based on selected characters. Molecular analysis identified two mitochondrial lineages that were syntopic (i.e., samples collected from the same locality in South Africa either grouped with clade one or two).The magnitude of divergence between-vs. within-clades was low (0.4-1%), but significant (FST: 0.84-0.88). Lack of apparent phylogeographic structure provides support for the absence of physical barriers to gene flow. Further, morphological analyses did not show any pattern of variation among lineages. The emergence and persistence of shallow mitochondrial divergence among sympatric lineages in Diederik Cuckoo may possibly be attributed to maternal divergence in host selection of these brood parasites.

Phenotypic correlates between clock genes and phenology among populations of Diederik cuckoo, Chrysococcyx caprius

“…With the exception of the Adcyap1 gene in the Southern population, tests of equilibrium showed no significant deviations which is indicative that allele frequencies may stay the same between generations (Hedrick, 1987 ) in the Northern ranges with some evidence of differentiation happening in the South; consistent with previous phylogenetic studies in this species using nuclear markers and mitochondrial DNA (Smith et al., 2023 ). A recent review on clock genes in migrating birds (Le Clercq, Bazzi, et al., 2023e ; Le Clercq, Bazzi, et al., 2023f ) found similar patterns of low heterozygosity and high homozygosity for populations in equilibrium for the Clock gene and higher heterozygosity for Adcyap1 .…”

“…Samples were partitioned based on subspecies, sex, migration timing and location. Sex was determined by molecular methods as previously described (Smith et al., 2023 ) and 21 males and nine females were assayed. Furthermore, samples were partitioned into birds who experienced increased activity early or late during their annual breeding cycles.…”

“…Species within the genus diverged approximately 7.71 MYA (diversification rate ( r ) = 0.24). The Diederik cuckoo is still classified as monotypic and results from detailed molecular study revealed no evidence of an emerging subspecies level divide between different populations based on neutral genomic markers and mitochondrial DNA (Smith et al., 2023 ). Although this species has been known for more than 300 years, little research has been conducted on them and many aspects of their life history and population structure remain uncharacterised.…”