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The use of virtual species to test species distribution models is important for understanding how aspects of the model development process influence model performance. Typically, virtual species are simulated by defining their niche as a function of environmental variables and simulating occurrence probabilistically via Bernoulli trials. This approach ignores endogenous processes known to drive species distribution such as dispersal and population dynamics. To understand whether these processes are important for simulating virtual species we compared the probabilistic simulation approach to those incorporating endogenous processes. This comparison was done by evaluating changes in the relationship between species occurrence and habitat suitability over a number of landscapes with varying spatial structure. We found that the combined effects of population dynamics and dispersal meant the probability of occurrence of a single cell was not only dependent on habitat suitability, but also the number of occupied cells nearby. This resulted in a dependence on the size of clusters of high suitability cells (analogous to patch size) to maintain populations, increased residual spatial autocorrelation and non‐stationarity of the species response between landscapes. These data characteristics are attributes of real species distribution data and are not present in probabilistic simulations. Researchers using virtual species should consider the importance of these characteristics to their study objectives to decide whether the inclusion of endogenous processes is necessary.

Background The current standard of treatment in primary biliary cholangitis (PBC) is ursodeoxycholic acid (UDCA), although a considerable proportion of patients show incomplete response resulting in disease progression. Objective This study aimed to assess the prevalence of incomplete response to UDCA and determine associated patients' characteristics. Methods Patients with PBC as main diagnosis were included from a national multicentric patient registry—Liver.pt. Main endpoints included incomplete response to UDCA treatment according to Barcelona, Paris I and Paris II criteria, Globe and UK PBC scores and the association between baseline characteristics and incomplete response according to Paris II criteria. Results A total of 434 PBC patients were identified, with a mean age of 55 years and 89.2% females. Nearly half of patients were asymptomatic at diagnosis and 93.2% had positive anti‐mitochondrial antibodies. Almost all patients (95.6%) had been prescribed at least one drug for PBC treatment. At the last follow‐up visit, 93.3% were under treatment of which 99.8% received UDCA. Incomplete response to UDCA was observed in 30.7%, 35.3%, 53.7% and 36.4% of patients according to Barcelona, Paris I, Paris II criteria and Globe score, respectively. After adjusting for age and sex, and accordingly to Paris II criteria, the risk for incomplete biochemical response was 25% higher for patients with cirrhosis at diagnosis (odds ratio [OR] = 1.25; 95% confidence interval [95%CI]: 1.02–1.54; p = 0.033) and 35% (95%CI:1.06–1.72; p = 0.016) and 5% (OR = 1.05; 95%CI:1.01–1.10; p = 0.013) for those with elevated gamma‐glutamyl transferase (GGT) and alkaline phosphatase (ALP). Conclusion A considerable proportion of patients showed incomplete biochemical response to UDCA treatment according to Paris II criteria. Cirrhosis, elevated GGT and ALP at diagnosis were identified as associated risk factors for incomplete response. Early identification of patients at risk of incomplete response could improve treatment care and guide clinical decision to a more careful patient monitorization., Key summary Summarise the established knowledge on this subject Primary biliary cholangitis is a liver disease that can progress to end‐stage liver disease, with premature death or need for liver transplantation.Treatment with ursodeoxycholic acid (UDCA) significantly increases liver transplant‐free survival. However, incomplete response to UDCA reduces this beneficial effect. What are the significant and/or new findings of this study? By evaluating prevalence and risk factors for UDCA incomplete response through a large multicentric national registry it was found that 53.7% of patients were incomplete responders, according to Paris II criteria, with cirrhosis, elevated gamma‐glutamyl transferase and alkaline phosphatase at diagnosis as the main risk factors.These findings suggest that patients diagnosed at an advanced stage should be closely monitored and might benefit from novel therapies to improve outcomes if incomplete response is present.