Differences in flowering sex ratios between native and invasive populations of the seagrass Halophila stipulacea

Deviations from the 1:1 sex ratio are common in dioecious plants. The tropical seagrass Halophila stipulacea is among an extremely rare group of dioecious plants that are widely recognized as female-biased. Here we report on differences in sex ratios between native (Eilat, northern Red Sea) and invasive (Cyprus, Mediterranean Sea) populations. While H. stipulacea populations were female-biased in their native region, invasive populations were either male-or female-biased. The existence of both sexes simultaneously in the Mediterranean invasive populations might help its ongoing expansion in the Mediterranean, thereby threatening local seagrasses species.