Where Speciation Biology and Conservation Biology Converge - Event Details

Where Speciation Biology and Conservation Biology Converge

Friday, November 1, 2024, 12:00pm – 1:00pm

Location: In-person at Wentworth Hall, Room 1, or online via Zoom at https://hawaii.zoom.us/j/99679339976 (passcode: TCBES)

Speaker: Dr. Elizabeth Stacy, Professor of Life Sciences, UNLV, Las Vegas, NV; UH Hilo TCBES Affiliate Faculty

"The ecology of hybrid incompatibilities in ʻŌhiʻa"

How isolating barriers accumulate during speciation is particularly poorly understood for long-lived, highly dispersible, landscape-dominant species, such as trees. Hawaiian Metrosideros (ʻŌhiʻa) is a rare example of adaptive radiation in trees that allows the study of isolating barriers at the early stages of speciation. I will introduce Hawaiian Metrosideros as a model for speciation research, present results from a recent study of hybrid incompatibilities (a form of postzygotic isolation) in this group, and draw inferences to the fate of Hawaii’s forests under climate change. We recently examined the performance under ambient and drought-stressed conditions of three sympatric taxa of Hawaiian Metrosideros from the island of Oʻahu, along with their (3) F1 and (6) backcross hybrid genotypes. The three taxa differ in morphology, patterns of resource allocation, and distribution along a steep rainfall gradient consistent with adaptation to contrasting levels of water availability [high elevation (wet), steep windy slopes (water-limited), low elevation (dry)]. All three taxa have high survivorship and fertility in the greenhouse, suggesting that greenhouse conditions are benign for these trees. We exposed 3-year-old saplings of the three taxa and the nine hybrid genotypes to a drought-recovery-drought regime in the greenhouse, monitoring photosynthesis and other traits. Under pre-drought conditions, only stomatal conductance and operating efficiency of photosystem 2 differed between the high- and low-elevation taxa, possibly consistent with differential adaptation to water availability. The three taxa showed substantial drought tolerance, but likely through contrasting mechanisms. In comparison with photosynthesis of the pooled parental taxa, that of the pooled backcross hybrids dropped significantly by the end of the first drought, continued to drop during the recovery period, and remained low through to the end of the experiment. Photosynthesis of the pooled F1 hybrids was either intermediate to parental and backcross levels or equal to that of the parentals at each phase of the experiment. The poor performance of backcross hybrids under drought is consistent with ecology-dependent hybrid incompatibilities, and these incompatibilities were manifest in all six backcross genotypes. These incompatibilities are among the first isolating barriers to emerge between diverging Metrosideros populations, and they likely have important consequences for Hawaiian forests under climate change given the abundance of hybrids in nature.

For more information, contact: canale@hawaii.edu (808) 932-7571

Tags: TCBES ʻŌhiʻa Dr. Elizabeth Stacy Wentworth Hall seminar Metrosideros Hawaiian trees