Towards the minimal conifer cone: ontogeny and trends in Cupressus, Juniperus and Microbiota (Cupressaceae s. str.)
Farjon, Aljos; Garcia, Sol; Ortiz,
published: Dec 19, 2002
Morphology and early development of seed cones of Cupressus goveniana Gordon, Juniperus phoenicea L., J. virginiana L., J. indica Bertol. and Microbiota decussata Kom. (Cupressaceae) have been studied under the Scanning Electron Microscope (SEM). The basic process of cone ontogeny is similar in all species observed. Their differences are due to differences in numbers of bracts (= cone scales) associated with ovules, differences in number of ovules produced, and the modifications in the bracts leading to mature cone scales. A tendency towards a reduction of these numbers, observable in the species studied, is interpreted as a probable evolutionary development. This hypothesis is supported by the probable phylogeny of the taxa. The selection pressures that possibly have led to this minimal cone are discussed. It would appear that this evolution to a minimal cone has occurred twice independently within Cupressaceae: once from a Cupressus-like cone to a 'monoseed' cone in Juniperus, and independently from Platycladus to Microbiota (JAGEL & STüTZEL 2001b), both these taxa not being closely related to the former.