Callitroideae

Callitroideae is a subfamily of plants within the cycad family (Cycadaceae), comprising approximately 150 species distributed across six genera. This group is characterized by its distinctive morphological and anatomical features, distinguishing it from other cycad subfamilies such as Zamioideae and Encephaloideae. Cycads are ancient vascular plants, with fossil records dating back to the Permian period, around 280 million years ago, making them one of the oldest seed plant lineages still in existence today.

The subfamily Callitroideae is primarily found in tropical and subtropical regions, with a notable concentration in Southeast Asia, Australia, and parts of Africa. Genera within this subfamily include *Ceratozamia*, *Dioon*, *Encephalartos*, *Macrozamia*, *Microcycas*, and *Zamia*, though *Encephalartos* is sometimes classified separately as its own subfamily. Species in Callitroideae exhibit a wide range of adaptations, including variations in leaf structure, cone morphology, and reproductive strategies.

Plants in this subfamily typically possess compound, fan-shaped or feather-like leaves, often arranged in a spiral pattern along the stem. The cones, which are the reproductive structures, can vary significantly in size and shape, with male cones usually larger than female cones. Pollination in cycads often relies on specific beetle species, which are attracted to the cones and facilitate fertilization.

Callitroideae species are of ecological and economic importance. Many are cultivated as ornamental plants due to their unique appearance and slow growth, which makes them popular in gardens and landscapes. Some species, particularly those in the genus *Encephalartos*, are endangered due to habitat destruction, illegal collection, and overharvesting for the international plant trade. Conservation efforts are ongoing to protect these ancient and ecologically significant plants.

The subfamily is also of scientific interest due to its evolutionary history and genetic diversity. Studies of Callitroideae contribute to broader understanding of plant reproduction, development, and adaptation, as well as the broader evolutionary relationships within cycads and seed plants.