Soft and sticky development: Some underlying reasons for microarchitectural pattern convergence

Surface sculpture of spores, pollen and other walled microscopic organisms commonly resembles patterns seen elsewhere in nature. These patterns are often species specific and of significant use in taxonomic study, particularly so in the fossil record where other data may be minimal. It can be argued that patterning, which must be governed to some extent by genotype, could simply reflect other natural patterns as a result of physical and chemical interaction during development. But does this diminish the view that patterning can often perform important biological functions? With examples drawn from fossil and living walled structures, we analyse the complex relationship between genetic constraints, construction mechanism and biological function, and we conclude that similar function may often result in similar pattern, perhaps further enhanced by similar aspects of development. The genetic complement, by way of selection, 'learns' to repeat the pattern, but each pattern creation mechanism retains a 'personal signature' reflecting its evolutionary history. With this new perspective in mind, we assess the potential implications in the study of Palaeozoic microfossils when many different groups are first developing surface patterning.