RUB » Evolution und Biodiversität der Pflanzen » Dr. Christian Schulz » Projects


Conifers, Selaginella, anatomy, morphology, systematics, phylogenetics, evolution, and biogeography


Research profile:
Originally trained as a morphologist, my first focus was on morphology and evolution of conifers. Over the years, I have extended my research to phylogeny and bioinformatics. During my PhD-time, I started working with the genus Selaginella (lycophytes). My current research focuses on evolution and biogeography of conifers and the genus Selaginella, including “relaxed” molecular clock approach, ancestral area reconstruction, and statistical analyses. The origin of these groups, their migration routes, and their long-distance dispersal events are particularly interesting to me. In my research I use SEM and microtome technique as well as bioinformatic and phylogenetic reconstruction techniques. Biodiversity research also includes the correct identification of species, which makes herbarium work and field trips necessary. In addition to my research, I teach courses on anatomy/morphology, phylogenetic reconstruction/bioinformatics, and biogeography (see CV).  Over the years, my experience with field trips and teaching taxonomy has helped me acquire extensive knowledge about plant species.  



1. Phylogeny, evolution, and biogeography of conifers

Gymnosperms can be divided into four major groups: conifers, cycads, Gnetidae and ginkgo. Conifers constitute the largest gymnosperm group, comprising about 850 taxa at species rank or lower and world-wide distribution. The earliest conifers date back to the Upper Carboniferous about 300 Myr ago; since then, conifers have conquered all continents. In this project, we are interested in the phylogeny of conifers, for example of Podocarpaceae (Knopf et al. 2012), DNA barcoding (Little et al. 2013), and which migration routes conifers have taken over time and space.


2. Morphology, systematics, evolution, and biogeography of the genus Selaginella

Lycophytes used to be dominant members of the world’s flora. Today, only three groups of lycophytes still exist: Selaginellaceae, Lycopodiaceae, and Isoetaceae. The genus Selaginella (spike-mosses) contains about 700 species, mainly distributed in the tropics and subtropics. Selaginella species are creeping or ascendant plants with simple, scale-like leaves on branching stems. The plants produce micro- and megaspore (heterospory). Lycophytes evolved in the Devonian about 400 Myr ago, and Selaginellaceae about 350 Myr ago. Reconstructing the migration routes of 350 Myr is an exciting challenge. Selaginella species are also interesting from the morphological and evolutionary perspective: e.g. due to their distinctive rhizophores, unique stem anatomy, and character-rich megaspores. Identification of Selaginella species is a big issue because they show high intraspecific – but low interspecific variability (Schulz et al. 2013). The character-rich surface sculpture of the megaspores facilitates identification of Selaginella species and makes identifications results more reliable.


3. The model species duo Selaginella apoda and Selaginella moellendorffii

Lycophytes, including the genus Selaginella, are one of the major land plant groups. Selaginella moellendorffii is the first sequenced non-seed vascular plant genome. The sequenced and annotated genome of Selaginella moellendorffii (Banks et al. 2011) provides opportunities to answer numerous questions, such as: How do MADS-box genes evolve from mosses via lycophytes (Selaginella moellendorffii) to angiosperms (Gramzow et al. 2012)? Selaginella apoda is an appropriate model species because of its short life cycle, ease of cultivation and many other useful characters (see table below). To work effectively with a model species, it is important to understand its morphology, anatomy, and life cycle in detail (Schulz et al. 2010a). Furthermore, a cultivation instruction is important for rapid and proactive work (Schulz et al. 2010b).The stages of a Selaginella apoda life cycle are also visualized in a video project.


4. MADS-box genes in Selaginella

One of the important transcription factors involved in the regulation of developmental processes are MADS-domain proteins. MADS-box genes are categorized into Type I and Type II; Type II can be further divided into MIKCc and MIKC* genes. Our examination of the complete genome sequence of a lycophyte, Selaginella moellendorffii, revealed 19 putative MADS-box genes (13 Type I, 3 MIKCc, and 3 MIKC*) (Banks et al. 2011). We could indicate that the most recent common ancestor of vascular plants possessed at least two Type I and two Type II genes. None of the Selaginella MADS-box genes are orthologous to floral organ identity genes in seed plants – which suggests that Selaginella MADS-box genes branched off before floral organ identity genes emerged (Gramzow et al. 2012).


5. Morphology, phylogeny, and evolution of Cupressaceae

In my diploma thesis, I investigated the particular position of ovules in the genus Juniperus, Cupressaceae (Schulz et al. 2003). Fascinated by the cypress family, I extended my research to the entire family. My work included the development of an identification key for the whole family, which can also be used for identification of Cupressaceae cultivars (Schulz et al. 2005).  Intra-specific variability has to be detected as a prerequisite for the development of an identification key and also for the interpretation of evolution of features.  Hence, the intra-specific variability was investigated in the whole family and the findings for the example of male cones were published (Schulz & Stützel 2006). Cone diversity in conifers is remarkable. We have been able to reveal the evolution of female cones in Cupressaceae (Schulz & Stützel 2007).