Environmental sex determination

[1] Environmental factors which often influence sex determination during development or sexual maturation include light intensity and photoperiod, temperature, nutrient availability, and pheromones emitted by surrounding plants or animals.

Environmental cues that often trigger the development of males or females include temperature, nutrient (or food in the case of animals) and water availability, photoperiod, competitive stress, and pheromones from conspecific individuals.

The amphipod crustacean Gammarus duebeni produces males early in the mating season, and females later, in response to the length of daylight, the photoperiod.

[9] The branchiopod crustacean Daphnia magna parthenogenetically produces male progeny in response to a combination of three environmental factors, namely a reduced photoperiod in autumn, shortage of food and raised population density.

Lacking genetic information coding for separate sexes, every fern spore has the capacity to become a male, female, or hermaphroditic gametophyte depending on the environment.

However, if no fertilization occurs, the female gametophyte can still become hermaphroditic and self-fertilize if the conditions are conducive to growth, ultimately resulting in inbreeding depression.

Additionally, similar to crocodilians, homosporous fern gametophyte sex is determined by the abiotic environment in accordance with the size-advantage model.

[22] In the presence of auxin, a widespread plant hormone, or gibberellins, compounds similar to Antheridiogen in ferns, both female and male individuals invest more in sexual structures (antheridia and archegonia).

Many angiosperms exhibit sequential hermaphroditism, meaning that they can switch sexes continually throughout their life based on the current conditions and resource availability to optimize fitness each flowering season.

The sex of the green spoonworm, Bonellia viridis , a marine annelid , depends on where the larvae make landfall (female shown).
The sex of alligators is determined by nest temperature.
A developing fern gametophyte. While in this immature, asexual stage, a fern gametophyte may undergo environmental sex determination based on cues from the surrounding environment.
Environmental sex determination in ferns based on nutrient availability, light, competition, and the pheromone Antheridiogen
Moss gametophytes (green photosynthetic tissue) and sporophytes (upright, brown structures). The presence of many sporophytes, indicates that the moss is likely either monoicous and self fertilizing or dioicous with fertile males and females. This can be rare as females often outcompete males in mosses.
Flowering catasetum viridiflavum