Rank-abundance curve for avian haemosporidian lineages at three altitudes in western Switzerland. Rank-abundance curve showing patterns of diversity for all avian haemosporidian parasite lineages found in three populations of great tits (Parus major) overall (black line), at low altitude (blue line), at intermediate altitude (red line) and at high altitude (green line). “Abundance” is defined as how prevalent parasites from each lineage are. The x-axis indicates lineage richness and the shape of the curve indicates evenness. The steeper the curve, the less evenly lineages are distributed (with a horizontal curve showing a completely evenly distributed system).