Pattern of Adaptive Divergence in Zingiber kawagoii Hayata (Zingiberaceae) along a Narrow Latitudinal Range

Abstract

Ecological and evolutionary processes linking adaptation to environment are related to species’ range shifts. In this study, we employed amplified-fragment-length-polymorphism-based genome scan methods to identify candidate loci among Zingiber kawagoii populations inhabiting varying environments distributed at low to middle elevations (143–1488 m) in a narrow latitudinal range (between 21.90 and 25.30° N). Here, we show evidence of selection driving the divergence of Z. kawagoii. Twenty-six FST outliers were detected, which were significantly correlated with various environmental variables. The allele frequencies of nine FST outliers were either positively or negatively correlated with the population mean FST. Using several independent approaches, we found environmental variables act in a combinatorial fashion, best explaining outlier genetic variation. Nonetheless, we found that adaptive divergence was affected mostly by annual temperature range, and it is significantly positively correlated with latitude and significantly negatively correlated with the population mean FST. This study addresses a latitudinal pattern of changes in annual temperature range (which ranged from 13.8 °C in the Lanyu population to 18.5 °C in the Wulai population) and emphasizes the pattern of latitudinal population divergence closely linked to the allele frequencies of adaptive loci, acting in a narrow latitudinal range. Our results also indicate environmentally dependent local adaptation for both leading- and trailing-edge populations.

The Contribution of Epigenetics to Evolutionary Adaptation in Zingiber kawagoii Hayata (Zingiberaceae) Endemic to Taiwan

“…This study used the same 17 populations of Z. kawagoii examined in an earlier investigation [ 23 ] ( Figure 1 ). Genomic DNA was extracted from silica gel dried leaf samples using a cetyltrimethyl ammonium bromide (CTAB) procedure [ 44 ], and ethanol-precipitated DNA was dissolved in 200 µL TE buffer (pH 8.0).…”

“…Genomic DNA was extracted from silica gel dried leaf samples using a cetyltrimethyl ammonium bromide (CTAB) procedure [ 44 ], and ethanol-precipitated DNA was dissolved in 200 µL TE buffer (pH 8.0). The 211 plants used in this study included all but one individual from the TRK population used in the earlier AFLP investigation [ 23 ] due to a technical problem. A NanoDrop spectrophotometer (NanoDrop Technology, Wilmington, DE, USA) was used to quantify total genomic DNA.…”

“…Sixteen environmental variables were included in this study [ 23 ]. These variables were annual temperate range (BIO7), mean temperature in the driest quarter (BIO9), annual precipitation (BIO12), precipitation in the coldest quarter (BIO19), aspect, elevation, slope, cloud cover (CLO), enhanced vegetation index (EVI), leaf area index (LAI), normalized difference vegetation index (NDVI), annual moisture index (MI), annual total potential evapotranspiration (PET), relative humidity (RH), soil pH, and mean wind speed (WS mean ) ( Table S2 ).…”

“…In an earlier study, using data on amplified fragment length polymorphism (AFLP), a latitudinal pattern of environmentally dependent adaptive genetic divergence was found to be highly correlated with the annual temperature range in Z. kawagoii [ 23 ]. It is probable that the latitudinal northerly range expansion of Z. kawagoii [ 24 ] may have been related to the latitudinal pattern of adaptive divergence in Z. kawagoii [ 23 ]. Additionally, the lack of genetic variation in Z. kawagoii [ 23 ] may result in genetic as well as migration load [ 25 , 26 ].…”

“…It is probable that the latitudinal northerly range expansion of Z. kawagoii [ 24 ] may have been related to the latitudinal pattern of adaptive divergence in Z. kawagoii [ 23 ]. Additionally, the lack of genetic variation in Z. kawagoii [ 23 ] may result in genetic as well as migration load [ 25 , 26 ]. Studies have demonstrated local adaptation linked to epigenetic variation and closely associated with environmental gradients in a variety of natural systems [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ].…”