A principal Element Occurrence (EO) represents the known extent of a species or ecosystem at a location, defined according to EO Specifications. A principal EO may be a single contiguous area or may be comprised of discrete patches or subpopulations. At the top of a nested relationship among EOs for a particular element, a principal EO can contain one or more sub-EOs. A principal EO containing sub-EOs is differentiated within the Details dialog by an additional Sub-EO accordion section.
Likewise, a sub-EO is differentiated within the Details dialog by the indication of Parent EO ID and the option to View Parent EO from the Tasks menu.
Within the data record of a Parent EO is evident by a Sub-EO Count > 0 within the Identifiers section.
Navigate to the Sub-EOs from the Related Record Menu via the Element Occurrence option by choosing Sub-EOs (1:n).
For species Elements, a principal Element Occurrence (EO) represents the occupied habitat (or previously occupied habitat) that contributes, or potentially contributes, to the persistence of the species at that location. Generally, a species principal EO corresponds to a population or metapopulation. Principal EOs are typically separated from each other by barriers to movement or dispersal, or by specific distances defined for each Element across either unsuitable habitat, or suitable but apparently unoccupied habitat.
For community Elements, a principal EO represents a defined area that contains (or contained) a characteristic species composition and structure. Principal EOs are separated from each other by barriers to species interactions, or by specific distances defined for each Element across adjacent areas occupied by other natural or semi-natural community types, or by cultural vegetation.
A principal EO may not necessarily provide knowledge of the full extent of the Element at that location. In such cases, only the portion of the occupied habitat or area that is known should be recorded from the evidence available (without extrapolation to include unsurveyed proximate habitat or area). The EO record should indicate whether the full extent of habitat or area occupied by the Element is known to be included in the principal EO using the Confidence Extent field.