Topology of syngameons

Abstract

Syngameons are sets of species linked by interspecific hybridization. Common observations regarding the structure of syngameons are that hybridization propensity is not uniform across species and that patterns of hybridization are dominated by a few species. I use computer simulations to test these claims in naturally occurring syngameons selected from the literature and from personal observation. Natural syngameons, especially those involving plants, typically exhibit nonrandom structure: The first three order statistics for the number of hybrid partners and the variance in the number of hybrid partners are larger than chance alone would predict. The structure of two insect syngameons examined is not significantly different from random. To test a hypothesis that variation in hybridization propensity across species in natural syngameons is simply an artifact of hybridization opportunity, I examine the structure of four artificial syngameons (fertility relationships) produced by full diallel crosses. Three of four artificial syngameons exhibit nonrandom structure, as the observed variation in number of successful crosses is larger than chance alone would predict. In general, there are no significant results involving the order statistics. Finally, I discuss biogeographic, ecological, and phylogenetic hypotheses for variation in hybridization propensity across species in natural syngameons.

Introgression across evolutionary scales suggests reticulation contributes to Amazonian tree diversity

“…These tests also recovered a geographically structured pattern of reticulation with three main centres: Ecuador, the Colombian Cordilleras and Venezuela. Geography has been shown to be a factor structuring syngameons, based simply on the increased opportunity of interbreeding when in sympatry (Boecklen, 2017). Two other significant introgression events were also inferred: one between B .…”

Crops, weeds and gathered plants in the vicinity of the mediaeval Castle Kolno, near Brzeg, S-W Poland, and a morphometric approach for some taxa

“…The term ''syngameon'' was used for the first time by J. P. Lotsy in 1917 to describe a complex unit of plant speciation (Ostenfeld 1918). Boecklen (2017) performed a computer simulation on the natural and artificial syngameons in plants and proved that their complexity correlates with the number of semi-species Fig. 10 A contemporary type of Prunus spinosa growing near the Kolno Castle and stones P. domestica subsp.…”

“…Fossils collected from the Kolno Castle can be used for performing such a morphometric analysis, which might provide data about changes induced by the man-made environments in useful plants. Plant species interacting reproductively in syngameons differ in their hybridisation potential, and hence, the hybridisation network between them is asymmetric and non-random (Grant 1981;Boecklen 2017). Analysis of this phenomenon in the man-induced syngameons will help us in better understanding the relationships between crops and their wild ancestors.…”

Genomic landscape of the global oak phylogeny

“…The botanical and evolutionary literature is rife with case studies of localized gene flow (Hardin, ; Whittemore & Schaal, ; McVay et al ., 2017a; Kim et al ., ) and ancient introgression (McVay et al ., 2017b; Kim et al ., ; Crowl et al ., ) in oaks. Oaks have in fact been held up as a paradigmatic syngameon (Hardin, ; Van Valen, ; Dodd & Afzal‐Rafii, ; Cannon & Scher, ; Boecklen, ; Cannon & Petit, ), a system of interbreeding species in which incomplete reproductive isolation may facilitate adaptive gene flow and species migration (Petit et al ., ; Dodd & Afzal‐Rafii, ; Leroy et al ., ). The oak genome (Plomion et al ., ) consequently tracks numerous unique species‐level phylogenetic histories that result from lineage sorting and differential rates of introgression (Anderson, ; Eaton et al ., ; McVay et al ., 2017b; Edelman et al ., ).…”