Traits represents a species' innate functions, abilities and personality. A species's traits are selected at the start of a new game, but a species or certain pops of a species can adapt new traits through genetic engineering or occasionally events. Traits affect a wide variety of areas, from population growth rate to resource output to lifespan or even how pops are viewed by other aliens. Most traits come in mutually exclusive groups that affect the same aspect of the species, such as Nomadic and Sedentary, and each pop can only have one such trait from the group at any given time. These groups include traits with opposite effects, as well as stronger variants of a trait. Though traits are initially decided at a species level, individual pops of the same species can end up with different traits with genetic modification, producing new subspecies or variants. This rarely happens without player intervention.
Traits are mostly fixed at the start of the game. Altering traits during the game is generally possible only later in the game through some select events or by using genetic engineering. Certain technologies and Ascension Perks add additional trait points that can be used to alter a part of your species' pops; modifications can range from altering their planet habitability to adding an additional positive trait or removing a negative one.
Traits are purchased from a points pool, with 2 points being available at the start of the game. Some traits are negative and have a negative cost, refunding points into the pool. Each species is limited to a maximum of 5 traits; non-standard traits do not count against this limit.
Initial traits are available when first creating a species. They can all be changed later via genetic modification.
Lithoid traits are only available to species with the Lithoid archetype. The Lithoid trait is always present on such species.
These traits are required for special cases of species and cannot be removed from the creation menu.
The Hive-Minded trait can only be added by hive mind empires and can only be removed by empires that are not hive minds. Pops with this trait in an non-Hive Mind empire will slowly die while pops without the Hive-Minded trait in a Hive Mind empire can only be displaced, purged or used as livestock.
Special traits that cost trait points can be removed via the biological ascension path. Special traits that do not cost trait points have a fixed chance of being inherited by hybrid species.
Biological ascension traits
There are 5 advanced traits which are made available for genetic modification if the Evolutionary Mastery ascension perk is taken and Genetic Resequencing has been researched. Biological ascension traits are only half as likely as standard traits to be inherited by hybrid species.
Pre-Sapient species have exclusive traits that cannot otherwise be chosen when creating or modifying a species. They retain these traits after being uplifted as a sapient species. All of these traits cost 1 trait point.
Each organic species also has a Habitability trait that determines their base habitability on the various types of worlds, usually that corresponding to the type of their homeworld. Habitability traits can be changed through genetic modification, but a pop can never have more than one Habitability trait.
The following habitability traits are not available for starting races:
All Robotic Pops have either the Mechanical or the Machine trait. Both traits grant +200% Habitability on all planets. Mechanical Pops can exist within Machine Intelligence empires via conquest but Machine Pops cannot exist outside Machine Intelligence empires. All Robotic Pops can then be given new traits through Robomodding, a few of them being restricted to Mechanical or Machine pops.