The inherent values of observation and description: A case study in the spiny solanums of Australia

The basic exploratory effort of doing descriptive biology is an avenue by which we can deepen our knowledge about taxa and the natural phenomena that drive their diversification. As Conniff (2011) wrote in The species seekers, "we still live in the great age of discovery", and much like that historically recognized period of the eighteenth and nineteenth centuries there remains today a distinct need for the sort of work that might have been attributable to the naturalists of that time. The careful observation of how organisms go about their lives, including how they interact with one another and the environments they occur in, can be a means to inspire and inform future work, to generate preliminary data, and to craft testable hypotheses about broad biological patterns. However, paying close attention to species and simply describing what they do is a worthwhile endeavor unto itself. This sort of inquiry has the additional potential to build capacity in fields like botany, where undergraduate and other early-stage students with access to plants in the field or in ex situ collections can easily experience the thrill of uncovering and describing something no one else has seen as clearly as they have. Large and diverse clades such as Solanum can be treasure troves of these sorts of discoveries. Solanum is one of the largest and most economically important plant genera, with some crop species garnering the focused attention of hundreds of individual scientists. And yet, as a diverse and variable genus there is still much to be learned. Mysteries abound, including the most basic natural history and biology of scores of poorly known species. We can never know everything, but there is still some importance in learning as much as we can manage—not only because of the inclusion in the genus of major food plants such as tomato, potato, and eggplant, but because Solanum is an ongoing evolutionary radiation of species and clades responding to recent ecological changes reflected in the Solanum floras on all continents except Antarctica. Given the proclivity of the genus for adapting to ecological variability (see Echeverría-Londoño & al., 2020), Solanum presents us with numerous infrageneric clades that might serve as models for observing how plants are and will respond to selective pressures across myriad scales, from plant-insect interactions to global shifts in climate and habitat loss. For two decades I have worked with students and postdocs on the spiny solanums of Australia (Leptostemonum clade/Hemigeacanthos clade, as per Deanna & al., in press), particularly a set of sub-arid tropical "bush tomatoes" that has radiated in at least partial response to climate oscillations beginning ca. 3 million years ago (Crisp & al., 2001). On this backdrop the "Solanum dioicum + Solanum echinatum group" (as per Martine & al., 2019) has diversified extensively, with ~45 described taxa and perhaps dozens of undescribed geographical variants rapidly radiating within the Australian Monsoon Tropics. The clade provides an example of the potential for applying observation and descriptive approaches to exceptional species groups within megadiverse genera as a means to foster impactful student research experiences. By focusing on a relatively small group through a number of different biological lenses, at times in response to individual student goals and interests, real insights can begin to accumulate. Sexual variation is one of the more intriguing areas of inquiry in our clade, with numerous species exhibiting each of three sexual systems: cosexuality, andromonoecy, and a functional form of dioecy in which "males" (used here as equivalent to "staminate") are morphologically and functionally staminate, but "females" (used here as equivalent to "pistillate") that present as morphologically cosexual (Fig. 1A) can only achieve "female" sexual function (fruits and seeds) because the pollen they make is inaperturate and thus non-germinable (see Anderson & Symon, 1989). Even within these "discrete" sexual systems, fluidity is common. For example, Solanum plastisexum Martine & McDonnell "is" andromonoecious but individual plants at times present as strictly "male" or strictly cosexual (McDonnell & al., 2019). In the dioecious taxa, "leaky male" flowers that present morphologically as functionally cosexual are fairly common and are now recorded for at least 10 species (Martine, 2023). The fascinating biology of sexual systems in this group is rife with opportunities for descriptive work, but this is just one category from a set of exceptional reproduction-related bush tomato "behaviors" that have generated student-driven exploratory outcomes of the sort mentioned above—nearly all of them made possible by establishing living ex situ collections originating from seeds acquired via germplasm collections or pulled from herbarium specimens. While these studies have been presented at conferences and, at times, submitted as theses, some (as iterative steps and paths to student development) have not so far been published in peer-reviewed journals. The production of inaperturate pollen in functionally "female" flowers (Fig. 1A) is an investment with obvious potential links to pollination biology, particularly given the lack of floral nectar in Solanum flowers (Symon & Anderson 1988), leading Ndem-Galbert & al. (2021) to conduct a study finding that the protein and amino acid rewards available to pollen-foraging bees are less abundant in inaperturate "female pollen" than the functional pollen produced by staminate individuals. Those results then inspired Carpenter & al. (2025) to establish an ongoing study focused on choice behavior of bees presented with the option of visiting either of the unisexual floral morphs. Driven by previous in situ observations of extra-floral nectar production on the leaves and abaxial corollas (Fig. 1B) of a few species (including S. cunninghamii Benth. and S. dioicum W.Fitzg.), Henry & al. (2025) established a project using high-performance liquid chromatography (HPLC) to assess the possibility that extra-floral nectar constituents are a function of plant-ant coadaptation. The coevolutionary links between bush tomatoes and animals represent a potential wellspring of new findings, including seed dispersal biology that is undocumented for nearly every species. Motter (2025) established greenhouse-based studies on a bush tomato (Solanum ossicruentum Martine & J.Cantley) hypothesized to use epizoochory via the production of trample burrs (Fig. 1C) (see Symon, 1984; Martine & al., 2016) and another (S. tudununggae Symon) suspected by Symon (1979) to employ a "censer mechanism" of wind dispersal. The general dearth of natural history knowledge surrounding the biology of recruitment in these Solanum taxa is an area of mostly unrealized inquiry, although Lacey & al. (2015) formulated food pellets containing S. asymmetriphyllum Specht seeds and found that the embryonic plants can survive rodent gut passage, and Garanich & al. (2016) tested the effects of fire, smoke, and temperature on seeds in S. beaugleholei Symon (Fig. 1D) and recorded limitations in seed germination at the highest temperatures. Beneroff & Martine (2025) later examined clonal spread mediated by belowground organs in a variant of S. dioicum, the first of many similar studies likely to come in this group where vegetative reproduction is commonplace. Established living collections of bush tomatoes have allowed for numerous crossing studies, including those testing the boundaries among species. Caton (2016) looked at the rate of success in crosses between two dioecious sister species, Solanum asymmetriphyllum and S. sejunctum Brennan & al., and then compared the morphology of the parents with resultant hybrids. This was followed by Hayes (2017), who conducted more than 4000 hand-pollinations among 20 different taxa to find that little reproductive isolation exists among the dioecious and andromonoecious species in the clade; and to infer, by virtue of self-crossing of "leaky" males, that genetic self-incompatibility is likely not present (in addition to unisexuality) among the dioecious species. Zizis (2023) then performed hundreds of crosses between the andromonoecious S. ultraspinosum A.R.Bean and the dioecious S. dioicum to track the breakdown of sexual systems across three generations of hybrid progeny. Noting the challenge of cultivating hundreds of greenhouse plants, Hayes & al. (2019) also developed a successful Integrated Pest Management scheme using predatory insects as a control for persistent pests. The idea that good science begins with good observations is obviously not new; it's the opening salvo for the very method. Nor is it a novel assertion that observation/exploration can be a means to inspire not only deeper thought and new ideas, but a more meaningful connection to nature and other species (e.g., Haskell, 2012)—particularly among students (e.g., Uno, 2009). This is, rather, a suggestion that the nightshades (and, in this particular case, the exceptional bush tomatoes of the Australian Monsoon Tropics) as well as other large and/or diverse clades of plants offer countless opportunities to make interesting and inherently important observational and descriptive inferences—which can then be parlayed into outcomes that may aid with student recruitment and retention, training opportunities for nascent botanists, and, with time, the measurable achievements that assist in career advancement for principle investigators. This might begin with the close examination of the life of a single species and simply asking the question, What don't we know about this plant? Often, the answer will be, A whole lot. Jason Cantley provided helpful comments. Much of the work cited herein was funded through support from one or more of the following: the David Burpee Endowment, the Wayne E. Manning Internship Fund, and the Biology Department at Bucknell University; and the Botanical Society of America Undergraduate Student Research Award.