Table 1.

Types and numbers of elements isolated with betaretrovirus reverse transcriptase degenerate primers from rodents with and without L1 activity^a

Species	No. of elements
	mysTR (no. with ORF)	IAP	β6	β
L1 inactive
Akodon boliviensis	12 (6)	1
Calomys callosus	13 (5)
Neacomys spinosus	14 (7)
Oryzomys palustris	9 (3)	2	5
L1 active
Nyctomys sumichrasti	17 (11)			1
Peromyscus maniculatus	23 (11)
Reithrodontomys fulvescens	17 (16)
Sigmodon hispidus	9 (5)	7

^aRT domains 1 to 4 (42) were aligned with those of previously identified mysTR sequences, the retroviruses seen in Fig. 3, and IAP, PyERV, and HTLV. A maximum likelihood search with 100 bootstraps resulted in the non-mysTR elements falling into clades within the betaretroviruses.