(A) Phylogenetic relationships among 54 FIV isolates determined (using BI, MP, and quartet-puzzling methods) on the basis of envelope V3-V4 region nucleotide sequences. A total of 501 nt positions were included for the tree reconstructions. The tree shown here is a consensus tree calculated from the best 9,000 BI trees. Statistical supporting values shown at major branches are PP (BI [from 9,000 best trees]), bootstrapping proportions (MP [from 1,000 replicates]), and puzzling indices (ML [with 10,000 puzzling steps]). Collapsed (unsupported) branches (as determined by MP and/or ML analysis) are marked by an x at corresponding positions. The strain names (GenBank accession numbers) for the V3-V4 sequences are as follows: EngUK8 (X69496); ScotUK2 (X69494); Wales UK14 (X69497); Wo (L06312); Dutch19K32 (M73965); USCAzepy01A (U02417); USCAhnky12A (U02403); USCAsam01A (U02410); USCAtt09A (U02413); SAP03 (AB010404); Sendai2 (D37814); Aomori 2 (D37817); Aomori 1 (D37816); Yokohama (D37812); AICO2 (AB010397); TY1 (D67064); USMAboy03B (U02419); USILbrny03B (U02418); USMOglwd03B (U02420); USTXmtex03B (U02422); M88 (Y13868); M2 (X69501); M3 (X69502); Lp9 (D84497); CABCpady02C (U02392); CABCpbar02C (U02394); CABCpbar03C (U02395); CABCpbar01C (U02393); CABCpbar07C (U02397); DEBAfredC (U57020); TI1 (AB016025); TI2 (AB016026); TI3 (AB016027); TI4 (AB016028); Fukuoka (D37815); Shizuoka (D37811); OKA01D (AB010400); Lp3 (D84496); Lp20 (D84498); Lp24 (D84500); TM2 (M59418); Usil2489_7B (U11820); Petaluma (M25381); PPR (M36968): TX125 (AY139094); TX120 (AY139095); TX200 (AY139096); TXMK (AY139097); TX133 (AY139098); TX132(AY139099); TX84 (AY139100); TXTG (AY139101); TX78 (AY139102); TX109 (AY139102); and TX77 (AY139103). (B) Consensus BI tree inferred from 27 capsid gene sequences with a total of 606 nt positions. PP values (BI [from 9,000 best trees]), bootstrapping proportions (MP [from 1,000 replicates]), and puzzling indices (ML [with 10,000 puzzling steps]) are shown at major branches. Collapsed branches (as determined by MP and/or ML analysis) are marked by an x at corresponding positions. The strain names (GenBank accession numbers) for the capsid sequences are as follows: Wo (L06136); Sendai1 (D37820); Z1 (X57001); Aomori2 (D37824); Sendai2 (D37821); Yokohama (D37819); Aomori1 (D37820); ItM3 (Y13866); ItM2 (Y13867); TI3 (AB027300); TI4 (AB027301); TI2 (AB027299); TI1 (AB027298); Shizuoka (D37822); Fukuoka (D37818); Lp24 (AB027304); Lp20 (AB027303); Lp3 (AB027302); TM2 (M59418); Usil2489_7B (U11820); Petaluma (M25381); PPR (M36968); TX120 (AY139105); TX77 (AY139106); TX78 (AY139107); TX84 (AY139108); TX53 (AY139109); TX200 (AY139110); TXTG (AY139111); and TX132 (AY139112).