A Rare Plant Population Has Been Observed on Catalina Island

CATALINA ISLAND— A team of Catalina Island Conservancy and partner botanists forayed into the Island’s fields to search for the very rare Santa Cruz Island rockcress (Sibara filifolia). The plant, federally listed as an endangered species, is tough to find, typically growing on dry south-facing slopes in coastal sage scrub habitats dominated by black sage (Salvia mellifera).

Surveys need to be done incredibly conscientiously.


“Currently, Sibara filifolia is known to occur in one general region of the island,” said Conservancy Rare Plant Ecologist Kevin Alison in an email to the Log. “However, our partners used geographical information systems (GIS) to develop maps that aim to predict other locations on the Island where the species could likely occur. The potential locations are based on factors that suggest suitable habitat for the species. These maps are exceptional tools for discovering new populations on the Island as we continue our management efforts.”


“Due to its small statue, thin vegetation, and cryptic colored leaves – especially when its flowers are not present,” said Alison in a news release. “Because it is so inconspicuous, we need to be especially careful not to trample or disturb the species or habitat,” said Alison.


Catalina Island Conservancy is part of a Sibara filifolia working group, a multi-organizational partnership invested in the survivorship of this species. This group includes government agencies, research institutions, and botanic gardens working toward plant conservation.


On the most recent survey, the Conservancy hosted a group of expert botanists from the Santa Barbara Botanic Garden to check previously known locations where Sibara filifolia was likely to occur.


“These collaborative partnerships are essential as this group can pool resources and expertise collectively toward achieving conservation goals of this endangered species,” added Alison. “This approach not only strengthens our ability to perform necessary data collection in the field but also work together as a team to interpret that data to inform our management decisions,” said Alison.


Each month from February to June, the Conservancy and partnering botanists set out to explore the slopes of Catalina, observe how the plants are doing over time and look for new populations on the Island.


“These surveys will allow us to better understand the distribution and ecology of the species on the island during their life cycle,” said Alison.


The Conservancy’s first survey was positive for the current populations of Sibara filifolia on Catalina. With these recent and consistent rains, researchers are seeing a significant amount of germination of new seedlings around the remains of plants compared to previous years. These elevated rain years leading to high germination rates are essential periods for the species to maintain healthy population sizes.


Though the Conservancy claims it is optimistic based on the initial survey results, it is still too early to tell if these findings will result in a sustainable population of Sibara fiifolia on Catalina Island.


“As seen in previous years, surveys, seasonal drought, and other events likely cause considerable mortality,” said Alison.


To secure the species long term, the Conservancy will collect and bulk seeds from these plant populations in collaboration with their partners.

“This will ensure a reliable source of plants are available to continue the propagation and conservation of this species,” said Alison.


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