Fertile Goeppertella from the Jurassic of Patagonia: mosaic evolution in the Dipteridaceae-Matoniaceae lineage.

Goeppertella has been postulated as a monophyletic group, whose precise position within the Gleichenoid families Dipteriaceae and Matoniaceae, remains poorly understood. Previously described Goeppertella specimens are based on frond fragments and its fertile morphology is represented by a few, poorly preserved specimens. We describe a new species based on the largest collection of fertile specimens known to date and discuss the evolutionary history of the genus based on the additional reproductive characters provided by the fossils described. Plant impressions were collected in Early Jurassic sediments of Patagonia, Argentina. The specimens were described, and silicone rubber casts were developed to examine in detail vegetative and reproductive features. The new species was compared with other Goeppertella species. Finally, a backbone analysis was performed in the context of a previously published combined matrix of Dipteridaceae, using the maximum parsimony criterion. The new species is described based on a combination of features that have not been previously reported. The vegetative morphology shows affinities with most fossil and extant Dipteriaceae, contrasting with the reproductive morphology which is more comparable with the scarce number of fossil dipteridaceous forms and it is more spread in the sister family, Matoniaceae. The backbone analysis indicates that the position of the new species vary among different positions among Dipteridaceae and Matoniaceae. Additional analyses, discriminating the signal of reproductive and vegetative character, are provided to discuss the base of this uncertainty. We consider Goeppertella as a member of the family Dipteridaceae since we interpret most shared features with Matoniaceae as plesiomorphic conditions for the family. In contrast, most shared features with Dipteridaceae represent apomorphies for the group. Thus, Goeppertella would represent an early diverging genus in Dipteridaceae, considering the venation characters as the most important in order to define the family.

Assessing the evolutionary history of the fern family Dipteridaceae (Gleicheniales) by incorporating both extant and extinct members in a combined phylogenetic study.

PREMISE OF THE STUDY: Dipteridaceae is a lineage of ferns that has existed from the early Mesozoic and is known for its extensive fossil record. By integrating information from all described extant and extinct genera into a single phylogenetic study, this paper aims to examine the taxonomy of the group on a whole and explore character evolution within the lineage across time. METHODS: A morphological matrix of 51 characters was developed for 72 species (43 extinct and 29 extant) based on published information. Morphological characters were combined with nucleotide sequences for four chloroplast genes (rbcL, atpA, atpB, and rps4) for extant taxa, and combined parsimony analyses were conducted to infer evolutionary trends in the group. KEY RESULTS: Dipteridaceae was found to be monophyletic and characterized by highly anastomosing minor veins forming a meshwork of areoles with free-included veinlets. Based on our analyses, we recognize six previously described genera (i.e., Goeppertella, Thaumatopteris, Clathropteris, Digitopteris, Dipteris, and Cheiropleuria) and one new genus (i.e., Sewardalea). Fossils currently described as Dictyophyllum, Kenderlykia, Hausmannia, and Protorhipis are ambiguously placed on the tree and are recognized as possibly unnatural morphogenera. CONCLUSIONS: Overall, the evolutionary trend in Dipteridaceae has been toward increasing complexity in the venation pattern and laminal fusion. Only the Hausmannia-type frond with dichotomizing primary veins and relatively fused lamina persisted in the later part of the Mesozoic to the present. Within the crown group, we see evidence of re-radiation of frond forms in Dipteris and Cheiropleuria.

Ontogenetic and temporal trajectories of chemical defence in a cyanogenic eucalypt.

Many studies have shown that similarly aged plants within a species or population can vary markedly in the concentration of defence compounds they deploy to protect themselves from herbivores. Some studies have also shown that the concentration of these compounds can change with development, but no empirical research has mapped such an ontogenetic trajectory in detail. To do this, we grew cyanogenic Eucalyptus yarraensis seedlings from three half-sibling families under constant glasshouse conditions, and followed their foliar cyanogenic glycoside (prunasin) concentration over time for 338 days after sowing (DAS). Plants in all families followed a similar temporal pattern. Plants increased in foliar prunasin concentration from a very low level (10 mug cyanide (CN) equivalents g(-1)) in their first leaves, to a maximum of, on average, 1.2 mg CN g(-1) at about 240 DAS. From 240 to 338 DAS, prunasin concentration gradually decreased to around 0.7 mg CN g(-1). Significant differences between families in maximum prunasin concentration were detected, but none were detected in the time at which this maximum occurred. In parallel with these changes in prunasin concentration, we detected an approximately linear increase in leaf mass per unit leaf area (LMA) with time, which reflected a change from juvenile to adult-like leaf anatomy. When ontogenetic trajectories of prunasin against LMA were constructed, we failed to detect a significant difference between families in the LMA at which maximum prunasin concentration occurred. This remarkable similarity in the temporal and ontogenetic trajectories between individuals, even from geographically remote families, is discussed in relation to a theoretical model for ontogenetic changes in plant defence. Our results show that ontogeny can constrain the expression of plant chemical defense and that chemical defense changes in a nonlinear fashion with ontogeny.