Abstract Detail

Population Genetics/Genomics

Hernandez, Adriana [1], Landis, Jacob [1], Specht, Chelsea [2].

The Population Dynamics and Evolutionary History of the Highly Polymorphic Calochortus venustus (Liliaceae).

The California endemic butterfly mariposa lily, Calochortus venustus L., displays striking variation in floral pigmentation and patterning, leading us to question the boundaries of species delimitation. Individuals within a population can range in petal color from a spectrum of red, purple, pink, white, and yellow, with variation in petal spots as well. This hyper-variability is only observed at the southern extent of its range, while northern populations are almost exclusively white. The phenotypic spatial distribution is suggestive of a ring species experiencing sequential change in phenotypic variation from the founding population, yet the population dynamics of its polymorphic nature had not been questioned prior to this study. Ring species are an ideal demonstration of incipient speciation, in which a founding population spreads and adapts in localized subpopulations separated across a divide and forming a ring such that when the farthest extending subpopulations come into contact, they can no longer interbreed. Leaf and floral tissue from 190 individuals spanning the natural geographic range around the central valley of California were collected in the field in 2019 for DNA extraction, each with quantified data on floral phenotype and geographic coordinates. A draft hybrid genome was assembled using long reads from an Oxford Nanopore minION and short reads from an Illumina NovaSeq 6000 to call SNPs using a reference guided RAD-Sequencing approach. The LEA package in R and PCA were then used for genetic clustering to compare floral phenotypic traits with particular genotypes (SNPs) and to infer population structure. These data were used in combination with calculated Fst values to characterize the evolutionary history among the identified populations. Results suggest phenotypic variation is not due to genetic differentiation, rather there is geographic cohesion within subpopulations and subpopulations have differentiated from each other likely due to isolation by distance. While genetic evidence does not suggest Calochortus venustus is a ring species, the largest genetic differentiation is between northern populations as expected based on phenotypic spatial distribution. Preliminary inference of phylogeographic history suggests a south to north range expansion around both sides of the California central valley, indicating parallel evolution toward the white morphotype in the northern range.

1 - Cornell University, Plant Biology and the L.H. Bailey Hortorium, School of Integrative Plant Science, 506 Mann Library Building, Ithaca, NY, 14850, USA
2 - Cornell University, School of Integrative Plant Science and L.H. Bailey Hortorium, 502 Mann Library, Ithaca, NY, 14850, USA

Keywords:
polymorphic traits
ring species
California Floristic Province
RAD-Sequencing
minION genome sequencing.

Presentation Type: Oral Paper
Session: POPGEN2, Population Genetics/Genomics II
Location: Virtual/Virtual
Date: Thursday, July 30th, 2020
Time: 3:00 PM
Number: POPGEN2001
Abstract ID:194
Candidate for Awards:Margaret Menzel Award